Castle Biosciences (CSTL) 10-K 10 Mar 20 2019 FY Annual report Financial data

Cover Page

Cover Page - USD ($)	12 Months Ended
	Dec. 31, 2019	Feb. 28, 2020	Jun. 30, 2019
Cover page.
Entity Registrant Name	CASTLE BIOSCIENCES INC
Entity Central Index Key	0001447362
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Ex-Transition Period	false
Entity Shell Company	false
Document Type	10-K
Document Period End Date	Dec. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Common Stock, Shares Outstanding		17,192,351
Entity Public Float			$ 0

BALANCE SHEETS

BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current Assets
Cash and cash equivalents	$ 98,845	$ 4,479
Accounts receivable, net	14,648	12,090
Inventory	1,237	882
Prepaid expenses and other current assets	1,951	675
Total current assets	116,681	18,126
Long-term accounts receivable, net	870	2,532
Property and equipment, net	2,060	1,529
Intangible assets, net	0	4
Other assets – long-term	135	214
Total assets	119,746	22,405
Current Liabilities
Accounts payable	1,865	1,451
Accrued compensation	5,779	4,571
Other accrued liabilities	1,812	715
Current portion of long-term debt	5,833	0
Total current liabilities	15,289	6,737
Long-term debt	19,289	24,500
Preferred stock warrant liability	0	1,194
Deferred rent liability	55	44
Total liabilities	34,633	32,475
Commitments and Contingencies (Note 11)
Stockholders’ Equity (Deficit)
Common stock, $0.001 par value; 200,000,000 and 15,102,000 shares authorized as of December 31, 2019 and 2018, respectively; 17,130,907 and 1,916,224 shares issued and outstanding as of December 31, 2019 and 2018, respectively.	17	2
Preferred stock, $0.001 par value; 10,000,000 and zero shares authorized as of December 31, 2019 and 2018, respectively; no shares issued and outstanding as of December 31, 2019 and 2018.	0	0
Additional paid-in capital	137,308	921
Accumulated deficit	(52,212)	(57,489)
Total stockholders’ equity (deficit)	85,113	(56,566)
Total liabilities, convertible preferred stock and stockholders’ equity (deficit)	119,746	22,405
Convertible preferred stock
Convertible Preferred Stock
Convertible preferred stock	0	1,501
Redeemable Convertible Preferred Stock Series A, B, D, E-1, E-2, E-2A, E-3 and F
Convertible Preferred Stock
Convertible preferred stock	$ 0	$ 44,995

BALANCE SHEETS (Parenthetical)

BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	200,000,000	15,102,000
Common stock, shares issued (in shares)	17,130,907	1,916,224
Common stock, shares outstanding (in shares)	17,130,907	1,916,224
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	10,000,000	0
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Convertible preferred stock
Convertible preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Convertible preferred stock, shares authorized (in shares)	0	503,056
Convertible preferred stock, shares issued (in shares)	0	503,056
Convertible preferred stock, shares outstanding (in shares)	0	503,056
Convertible preferred stock, aggregate liquidation	$ 0	$ 2,417
Redeemable Convertible Preferred Stock Series A, B, D, E-1, E-2, E-2A, E-3 and F
Convertible preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Convertible preferred stock, shares authorized (in shares)	0	9,640,493
Convertible preferred stock, shares issued (in shares)	0	9,456,775
Convertible preferred stock, shares outstanding (in shares)	0	9,456,775
Convertible preferred stock, aggregate liquidation	$ 0	$ 57,570

STATEMENTS OF OPERATIONS AND CO

STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (LOSS) - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
NET REVENUES	$ 51,865	$ 22,786
COST OF SALES	7,310	5,297
Gross margin	44,555	17,489
OPERATING EXPENSES
Research and development	7,385	4,854
Selling, general and administrative	29,842	16,471
Total operating expenses	37,227	21,325
Operating income (loss)	7,328	(3,836)
Interest income	312	24
Interest expense	(4,571)	(2,274)
Gain on extinguishment of debt (Note 7)	5,213	0
Other expense, net	(2,933)	(272)
Income (loss) before income taxes	5,349	(6,358)
Income tax expense	72	9
Net income (loss) and comprehensive income (loss)	5,277	(6,367)
Net income (loss) and comprehensive income (loss)	5,277	(6,367)
Convertible preferred stock cumulative dividends	2,156	3,577
Accretion of redeemable convertible preferred stock to redemption value	130	219
Net income (loss) and comprehensive income (loss) attributable to common stockholders	$ 2,991	$ (10,163)
Earnings (loss) per share attributable to common stockholders:
Basic (in dollars per share)	$ 0.35	$ (5.33)
Diluted (in dollars per share)	$ (0.21)	$ (5.33)
Weighted-average shares outstanding:
Basic (in shares)	8,584	1,906
Diluted (in shares)	8,658	1,906

STATEMENTS OF CONVERTIBLE PREFE

STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Convertible preferred stock	Redeemable Convertible Preferred Stock Series A, B, D, E-1, E-2, E-2A, E-3 and F	Series E-1	Series E-2A	Series E-3	Series F	Common Stock	Preferred Stock	Additional Paid-in Capital	Additional Paid-in CapitalSeries E-1	Additional Paid-in CapitalSeries E-2A	Additional Paid-in CapitalSeries E-3	Additional Paid-in CapitalSeries F	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2017		503,056	7,611,010
Beginning balance at Dec. 31, 2017		$ 1,501	$ 34,538
Increase (Decrease) in Temporary Equity [Roll Forward]
Issuance of Series F redeemable convertible preferred stock (in shares)							1,809,564
Issuance of Series F redeemable convertible preferred stock							$ 9,990
Accretion of redeemable convertible preferred stock to redemption value:				$ 4	$ 1	$ 12	$ 203
Exercise of redeemable convertible preferred stock warrants (in shares)				3,250			32,951
Exercise of redeemable convertible preferred stock warrants				$ 15			$ 232
Ending balance (in shares) at Dec. 31, 2018		503,056	9,456,775	829,642	27,306	824,000	4,734,613
Ending balance at Dec. 31, 2018		$ 1,501	$ 44,995	$ 3,099	$ 125	$ 4,394	$ 27,174
Beginning balance (in shares) at Dec. 31, 2017								1,896,469	0
Beginning balance at Dec. 31, 2017	$ (50,311)							$ 2	$ 0	$ 809					$ (51,122)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock compensation expense	$ 294									294
Exercise of common stock options (in shares)	19,755							19,755
Exercise of common stock options	$ 38							$ 0		38
Accretion of redeemable convertible preferred stock to redemption value				(4)	$ (1)	(12)	(203)				$ (4)	$ (1)	$ (12)	$ (203)
Net income (loss)	(6,367)														(6,367)
Ending balance (in shares) at Dec. 31, 2018								1,916,224	0
Ending balance at Dec. 31, 2018	(56,566)							$ 2	$ 0	921					(57,489)
Increase (Decrease) in Temporary Equity [Roll Forward]
Accretion of redeemable convertible preferred stock to redemption value:				$ 2		7	$ 121
Exercise of redeemable convertible preferred stock warrants (in shares)				12,999			1,054
Exercise of redeemable convertible preferred stock warrants				$ 107			$ 10
Conversion of convertible preferred stock (in shares)		(503,056)	(9,470,828)					8,181,992
Conversion of convertible preferred stock	46,743	$ (1,501)	$ (45,242)					$ 8		46,735
Ending balance (in shares) at Dec. 31, 2019		0	0
Ending balance at Dec. 31, 2019		$ 0	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock compensation expense	$ 1,249									1,249
Exercise of common stock options (in shares)	693,127							693,140
Exercise of common stock options	$ 1,175							$ 1		1,174
Exercise of common stock warrants (in shares)								51,238
Exercise of common stock warrants	0
Accretion of redeemable convertible preferred stock to redemption value				$ (2)		$ (7)	$ (121)				$ (2)		$ (7)	$ (121)
Recognition of beneficial conversion feature on convertible promissory notes	8,378									8,378
Extinguishment of beneficial conversion feature on convertible promissory notes	(15,265)									(15,265)
Initial public offering of common stock, net of underwriting discounts, commissions and offering costs (in shares)								4,600,000
Initial public offering of common stock, net of underwriting discounts, commissions and offering costs	65,931							$ 5		65,926
Conversion of convertible promissory notes (in shares)								1,661,106
Conversion of convertible promissory notes	26,577							$ 1		26,576
Conversion of convertible preferred stock (in shares)		(503,056)	(9,470,828)					8,181,992
Conversion of convertible preferred stock	46,743	$ (1,501)	$ (45,242)					$ 8		46,735
Reclassification of preferred stock warrant liability and net exercise of certain warrants in connection with initial public offering (in shares)								27,207
Reclassification of preferred stock warrant liability and net exercise of certain warrants for common stock in connection with initial public offering	1,744							$ 0		1,744
Net income (loss)	5,277														5,277
Ending balance (in shares) at Dec. 31, 2019								17,130,907	0
Ending balance at Dec. 31, 2019	$ 85,113							$ 17	$ 0	$ 137,308					$ (52,212)

STATEMENTS OF CASH FLOWS

STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
OPERATING ACTIVITIES
Net income (loss)	$ 5,277	$ (6,367)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation	354	287
Stock compensation expense	1,249	294
Amortization of intangibles	4	36
Amortization of debt discounts and issuance costs	1,925	566
Other non-cash interest	442	0
Gain on extinguishment of debt	(5,213)	0
Change in fair value of preferred stock warrant liability	619	272
Change in fair value of embedded derivative	237	0
Change in fair value of convertible promissory note accounted for under the fair value option	2,077	0
Other	0	(24)
Change in operating assets and liabilities:
Accounts receivable	(896)	(8,408)
Prepaid expenses and other current assets	(1,276)	(160)
Inventory	(355)	(578)
Other assets	(85)	14
Accounts payable	557	197
Accrued compensation	1,208	1,347
Other accrued liabilities	879	201
Deferred rent liability	12	28
Net cash provided by (used in) operating activities	7,015	(12,295)
INVESTING ACTIVITES
Purchases of property and equipment	(937)	(277)
Net cash used in investing activities	(937)	(277)
FINANCING ACTIVITIES
Proceeds from initial public offering of common stock, net of underwriting discounts, commissions and issuance costs	65,931	0
Proceeds from issuance of preferred stock and preferred stock warrants (including exercised warrants)	49	10,383
Proceeds from issuance of term debt and preferred stock warrants, net of issuance costs	0	4,418
Proceeds from issuance of convertible promissory notes (including $4,756 from related parties), net of issuance costs	11,695	0
Proceeds from issuance of convertible promissory note and common stock warrant, net of issuance costs	9,236	0
Proceeds from issuance of term debt, net of issuance costs	1,776	0
Proceeds from line of credit	0	1,000
Repayments on line of credit	(1,791)	0
Proceeds from exercise of common stock options	1,174	38
Proceeds from contributions to the employee stock purchase plan	218	0
Net cash provided by financing activities	88,288	15,839
NET CHANGE IN CASH AND CASH EQUIVALENTS	94,366	3,267
Beginning of period	4,479	1,212
End of period	98,845	4,479
SUPPLEMENTAL DISCLOSURE OF CASH PAID (REFUNDED) FOR:
Interest	2,206	1,635
Income taxes	(150)	160
DISCLOSURE OF NON-CASH INVESTING AND FINANCING ACTIVITIES:
Accrued capital expenditures	7	58
Initial public offering costs incurred but not paid	0	91
Issuance of common stock upon conversion of convertible preferred stock	46,743	0
Conversion of preferred stock warrants to common stock warrants	1,745	0
Issuance of common stock upon conversion of convertible promissory notes	26,578	0
Cashless exercise of common stock warrants	$ 455	$ 0

STATEMENTS OF CASH FLOWS (Paren

STATEMENTS OF CASH FLOWS (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)
Statement of Cash Flows [Abstract]
Proceeds from issuance of convertible promissory notes from related parties	$ 4,756

Organization and Description of

Organization and Description of Business	12 Months Ended
	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Description of Business	Organization and Description of Business Castle Biosciences, Inc. (the ‘‘Company’’) was incorporated in the state of Delaware on September 12, 2007. The Company is a commercial-stage dermatological cancer company focused on providing physicians and their patients with personalized, clinically actionable genomic information to make more accurate treatment decisions. The Company is based in Friendswood, Texas (a suburb of Houston, Texas) and its laboratory operations are conducted at the Company’s facility located in Phoenix, Arizona. On July 11, 2019, the Company effected a 1-for-1.219 reverse stock split of its common stock. The par value and the authorized number of shares of common stock were not affected by the reverse stock split. The reverse stock split resulted in an adjustment to the Series A, B, C, D, E-1, E-2, E-2A, E-3, and F preferred stock conversion prices to reflect a proportional decrease in the number of shares of common stock to be issued upon conversion. The accompanying financial statements and notes to the financial statements give retroactive effect to the reverse stock split for all periods presented. On July 29, 2019, the Company completed the initial public offering of its common stock (the “IPO”). In the IPO, the Company issued and sold 4,600,000 shares of its common stock, including 600,000 shares sold pursuant to the full exercise of the underwriters’ option to purchase additional shares, at a price to the public of $16.00 per share. The Company received approximately $65.9 million in net proceeds, after deducting underwriting discounts and commissions and other offering expenses payable by the Company. In connection with the IPO, on July 29, 2019 all convertible preferred stock and all convertible promissory notes converted into shares of common stock and all outstanding warrants to purchase shares of convertible preferred stock became exercisable for shares of common stock. Liquidity and Capital Resources The Company has incurred significant operating losses since its inception. As of December 31, 2019 , the Company had an accumulated deficit of $52.2 million and cash and cash equivalents totaling $98.8 million . The Company also has substantial indebtedness, the terms of which require it to meet a three-month trailing revenue covenant tested quarterly (previously a six-month trailing revenue covenant and tested monthly, as described below). At the time of issuance of the Company’s financial statements as of December 31, 2018 and 2017 and for each of the years then ended, the Company disclosed that substantial doubt was raised about the Company’s ability to continue as a going concern, because its projections indicated potential non-compliance with this covenant during the next 12 months. Subsequently, as discussed in Note 8, “Long-Term Debt,” on June 13, 2019, the Company entered into an amendment to its debt agreement, which among other changes, modified the revenue covenant from a trailing six-month calculation to a trailing three-month calculation with revised revenue targets tested monthly. In February and March 2020, the Company entered into amendments of the 2018 LSA with the Lenders that, among other things, changed the covenant from being tested monthly to quarterly testing and established revenue targets for the year ending December 31, 2020. Management now expects to be in compliance with the covenant during the next 12 months. The Company intends to fund planned operations for the next 12 months using its cash on hand, including net cash proceeds from the IPO, and collections from test report sales.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation The Company’s financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (‘‘U.S. GAAP’’). The Company has no subsidiaries and all operations are conducted by the Company. Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Significant items subject to such estimates include revenue recognition, the determination of fair value of the Company’s preferred stock warrants and convertible debt embedded derivatives, the valuation of stock options, assessing future tax exposure and the realization of deferred tax assets, the useful lives and recoverability of property and equipment, and contingent liabilities. The Company bases these estimates on historical and anticipated results, trends, and various other assumptions that the Company believes are reasonable under the circumstances, including assumptions as to future events. These estimates form the basis for making judgments about the carrying values of assets and liabilities and recorded revenues and expenses that are not readily apparent from other sources. Actual results could differ from those estimates and assumptions. Operating Segments Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision maker, or decision-making group, in making decisions on how to allocate resources and assess performance. The Company views its operations and manages its business as one operating segment. All revenues are attributable to U.S.-based operations and all assets are held in the United States. Cash and Cash Equivalents including Concentrations of Credit Risk Cash equivalents consist of short-term, highly liquid investments with original maturities of three months or less. Cash equivalents consist primarily of amounts invested in money market accounts. A majority of the Company’s cash and cash equivalents are deposited with a single financial institution. Deposits in this institution may exceed the amount of insurance provided on such deposits by the Federal Deposit Insurance Corporation for U.S. institutions. The Company has not experienced any losses on its deposits of cash and cash equivalents. Management believes that the Company is not exposed to significant credit risk due to the financial position of the depository institutions in which those deposits are held. Revenue Recognition Revenue is recognized in accordance with Financial Accounting Standards Board (‘‘FASB’’) Accounting Standards Codification (‘‘ASC’’) Topic 606, Revenue from Contracts with Customers (‘‘ASC 606’’). In accordance with ASC 606, the Company follows a five-step process to recognize revenues: (1) identify the contract with the customer, (2) identify the performance obligations, (3) determine the transaction price, (4) allocate the transaction price to the performance obligations and (5) recognize revenues when the performance obligations are satisfied. All of the Company’s revenues from contracts with customers are associated with the provision of diagnostic and prognostic cancer testing services. Most of the Company’s revenues are attributable to DecisionDx-Melanoma for cutaneous melanoma. The Company also provides a test for uveal melanoma, DecisionDx-UM. Information on the disaggregation of revenues by the Company’s significant third-party payors is included under Payor Concentration below. The Company has determined that it has a contract with the patient when the treating clinician orders the test. The Company’s contracts generally contain a single performance obligation, which is the delivery of the test report, and the Company satisfies its performance obligation at a point in time upon the delivery of the test report to the treating physician, at which point the Company can bill for the report. The amount of revenue recognized reflects the amount of consideration to which the Company expects to be entitled (the ‘‘transaction price’’) and considers the effects of variable consideration, which is discussed further below. Once the Company satisfies its performance obligations and bills for the service, the timing of the collection of payments may vary based on the payment practices of the third-party payor and the existence of contractually established reimbursement rates. Most of the payments for the Company’s services are made by third-party payors, including Medicare and commercial health insurance carriers. Certain contracts contain a contractual commitment of a reimbursement rate that differs from the Company’s list prices. However, absent a contractually committed reimbursement rate with a commercial carrier or governmental program, the Company’s diagnostic tests may or may not be covered by these entities’ existing reimbursement policies. In addition, patients do not enter into direct agreements with the Company that commit them to pay any portion of the cost of the tests in the event that their insurance provider declines to reimburse the Company. The Company may pursue, on a case-by-case basis, reimbursement from such patients in the form of co-payments and co-insurance, in accordance with the contractual obligations that the Company has with the insurance carrier or health plan. These situations may result in a delay in the collection of payments. The Medicare claims that are covered by policy under a Local Coverage Determination (‘‘LCD’’) are generally paid at the established rate by the Company’s Medicare contractor within 30 days from receipt. Medicare claims that were either submitted to Medicare prior to the LCD coverage commencement date or are not covered by the terms of the LCD but meet the definition of being medically reasonable and necessary pursuant to the controlling Section 1862(a)(1)(A) of the Social Security Act are generally appealed and may ultimately be paid at the first (termed ‘‘redetermination’’), second (termed ‘‘reconsideration’’) or third level of appeal (de novo hearing with an Administrative Law Judge (“ALJ”)). A successful appeal at any of these levels results in payment. In the absence of LCD coverage or contractually established reimbursements rates, the Company has concluded that its contracts include variable consideration because the amounts paid by Medicare or commercial health insurance carriers may be paid at less than the Company’s standard rates or not paid at all, with such differences considered implicit price concessions. Variable consideration attributable to these price concessions is measured at the expected value using the ‘‘most likely amount’’ method under ASC 606. The amounts are determined by historical average collection rates by test type and payor category taking into consideration the range of possible outcomes, the predictive value of the Company’s past experiences, the time period of when uncertainties expect to be resolved and the amount of consideration that is susceptible to factors outside of the Company’s influence, such as the judgment and actions of third parties. Such variable consideration is included in the transaction price only to the extent it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur when the uncertainties with respect to the amount are resolved. Variable consideration may be constrained and excluded from the transaction price in situations where there is no contractually agreed upon reimbursement coverage or in the absence of a predictable pattern and history of collectability with a payor. Variable consideration for Medicare claims is deemed to be fully constrained when the payment of such claims is subject to approval by an ALJ at an appeal hearing, due to factors outside the Company’s influence (i.e., judgment or actions of third parties) and the uncertainty of the amount to be received is not expected to be resolved for a long period of time. Variable consideration is evaluated each reporting period and adjustments are recorded as increases or decreases in revenues. Included in revenues for the years ended December 31, 2019 and 2018 were $2,493,000 and $343,000 , respectively, of revenue increases associated with changes in estimated variable consideration related to performance obligations satisfied in previous periods. These amounts include (i) adjustments for actual collections versus estimated amounts and (ii) cash collections and the related recognition of revenue in current period for tests delivered in prior periods due to the release of the constraint on variable consideration. Because the Company’s contracts with customers have an expected duration of one year or less, the Company has elected the practical expedient in ASC 606 to not disclose information about its remaining performance obligations. Any incremental costs to obtain contracts are recorded as selling, general and administrative expense as incurred due to the short duration of the Company’s contracts. Contract balances consisted solely of accounts receivable (both current and noncurrent) as of December 31, 2019 and 2018 . DecisionDx-Melanoma Claims Consolidation In June 2017, the Company submitted to the Office of Medicare Hearings and Appeals (‘‘OMHA’’) a formal request to participate in a program that OMHA developed with the intent of providing appellants a means to have large volumes of claim disputes adjudicated at an accelerated rate. The program consolidates outstanding claims at the ALJ level and uses a statistical-sampling approach where five ALJ’s will determine reimbursement results for a sample of claims which are then extrapolated to the universe of claims. The consolidation includes 2,698 DecisionDx-Melanoma claims dating from 2013 through spring 2017. The judges who will review the sample sets have been identified and the hearings were held in April 2019 with a supplemental hearing in May 2019. No formal ruling has been issued to date. In accordance with ASC 606, the Company has not recognized (fully constrained the variable consideration) any revenues attributable to these claims in its financial statements pending the outcome of this matter. The Company expects to recognize any revenue adjudicated by the ALJ in the periodic reporting period in which the Company is notified of the ALJ hearing outcome and it is determined that such decision will not be appealed. Payor Concentration The Company relies upon reimbursements from third-party government payors (primarily Medicare) and private-payor insurance companies to collect accounts receivable related to sales of its diagnostic tests. The Company’s significant third-party payors and their related revenues as a percentage of total revenues and accounts receivable balances are as follows: Percentage of Revenues Percentage of Accounts Receivable (current) Percentage of Accounts Receivable (non-current) Year Ended December 31, As of December 31, As of December 31, 2019 2018 2019 2018 2019 2018 Medicare 49 % 36 % 7 % 54 % — % — % Medicare Advantage plans 29 % 17 % 41 % 9 % 18 % 18 % United Healthcare 6 % 12 % 9 % 7 % — % 15 % BlueCross BlueShield plans 6 % 18 % 25 % 18 % 46 % 41 % Accounts Receivable and Allowance for Doubtful Accounts The Company classifies accounts receivable balances that are expected to be paid more than one year from the balance sheet date as non-current assets. The estimated timing of payment utilized as a basis for classification as non-current is determined by analyses of historical payor-specific payment experience, adjusted for known factors that are expected to change the timing of future payments. The Company accrues an allowance for doubtful accounts against its accounts receivable when it is probable that an account is not collectible, based on write off history, credit risk of specific accounts, aging analysis and other information available on specific accounts. The Company generally does not perform evaluations of customers’ financial condition and generally does not require collateral. Accounts receivable are written off when all efforts to collect the balance have been exhausted. Historically, the Company’s bad debt expense has not been significant. The allowance for doubtful accounts was zero as of December 31, 2019 and 2018 . Adjustments for implicit price concessions attributable to variable consideration, as discussed above, are incorporated into the measurement of the accounts receivable balances and are not part of the allowance for doubtful accounts. Inventory The Company carries an inventory of test supplies in the Phoenix, Arizona laboratory. The inventory is carried at the lower of weighted average cost and net realizable value and expensed through cost of sales as the supplies are used. Property and Equipment Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation is computed using the straight-line method over the estimated useful lives of the assets, generally between five and ten years . Leasehold improvements are amortized using the straight-line method over the shorter of the estimated useful life of the asset or the term of the lease. The Company’s leasehold improvements primarily relate to its office and laboratory in Phoenix, Arizona, and are generally being amortized through the end of the lease term in July 2027. Maintenance and repairs are charged to expense as incurred, and material improvements are capitalized. When assets are retired or otherwise disposed of, the cost and accumulated depreciation are removed from the balance sheet and any resulting gain or loss is reflected in the statements of operations and comprehensive loss in the period realized. Patent Rights Licenses The Company capitalizes the purchase of material licenses that grant interest in and to certain patent rights owned primarily by research and education institutions. These costs are amortized using the straight-line method over the shorter of the period of expected commercial benefit or the life of the underlying patent. Amortization of patent license costs is charged to research and development expense. Long-Lived Assets The Company reviews long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of the assets may not be recoverable. An impairment loss is recognized when the total of estimated future undiscounted cash flows, expected to result from the use of the asset and its eventual disposition, are less than the carrying amount. Impairment, if any, would be calculated based on the excess of the carrying amount of the long-lived asset over the long-lived asset’s fair value. There were no impairment charges recognized for the years ended December 31, 2019 and 2018. Fair Value of Financial Instruments The carrying amount of the Company’s long-term debt approximates fair value due to its variable market interest rate and management’s opinion that current rates and terms that would be available to the Company with the same maturity and security structure would be essentially equivalent to that of the Company’s long-term debt. This estimated fair value is a ‘‘Level 3’’ fair value measurement, as defined in Note 10. Deferred Rent The Company has negotiated certain landlord/tenant incentives, rent holidays and escalations in the base price of rent payments under operating leases. The Company recognizes these incentives, rent holidays and rent escalations on a straight-line basis over the lease term. Deferred rent balances are classified as current or non-current in the accompanying balance sheets based upon the period when reversal of the liability is expected to occur. Cost of Sales Cost of sales is expensed as incurred and includes direct labor costs, equipment, supplies, materials and infrastructure expenses associated with testing tissue samples, third-party lab processing and service costs, third-party collection costs, and shipping charges to transport samples. Research and Development Research and development costs are charged to operations as incurred. Advance payments for goods and services that will be used in future research and development activities are expensed when the activity has been performed or when the goods have been received rather than when the payment is made. Upfront and milestone payments due to third parties that perform research and development services on behalf of the Company will be expensed as services are rendered or when the milestone is achieved. Research and development costs include, but are not limited to, payroll and personnel-related expenses, stock-based compensation expense, materials, laboratory supplies, and consulting costs. Selling, General and Administrative Expenses Selling, general and administrative (“SG&A”) expenses are attributable to sales, marketing, executive, finance and accounting, legal and human resources functions. These expenses consist of personnel costs (including salaries, employee benefit costs, bonuses and equity-based compensation expenses), customer services expenses, direct marketing expenses, educational and promotional expenses, market research, audit and legal expenses, and consulting. The Company expenses all SG&A costs as incurred. Accrued Compensation The Company accrues for liabilities under discretionary employee and executive bonus plans. These estimated compensation liabilities are based on progress against corporate objectives approved by the Board of Directors, compensation levels of eligible individuals, and target bonus percentage levels. The Board of Directors reviews and evaluates the performance against these objectives and ultimately determines what discretionary payments are made. The Company also accrues for liabilities under employee sales incentive bonus plans with accruals based on performance achieved to date compared to established targets. As of December 31, 2019 and 2018 , the Company accrued approximately $4,785,000 and $3,197,000 , respectively, for liabilities associated with these bonus plans. These amounts are classified as current or noncurrent accrued liabilities in the balance sheets based on the expected timing of payment. Retirement Plan The Company has an Internal Revenue Code (“IRC”) Section 401(k) profit sharing plan (the “Plan”) for eligible employees. The Plan is funded by employee contributions and provides for discretionary contributions in the form of matching and/or profit-sharing contributions. For the years ended December 31, 2019 and 2018, the Company provided a discretionary matching contribution of $434,000 and $338,000 , respectively. Income Taxes The Company recognizes deferred tax assets and liabilities for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using statutory tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in the period that includes the statutory enactment date. Valuation allowances are established to reduce deferred tax assets when it is more likely than not that some portion or all of the deferred tax assets will not be realized. Tax benefits are recognized only for tax positions that are more likely than not to be sustained upon examination by tax authorities. The amount recognized is measured as the largest amount of benefit that is greater than 50% likely to be realized upon settlement. A liability for unrecognized tax benefits is recorded for any tax benefits claimed in the Company’s tax returns that do not meet these recognition and measurement standards. The Company’s policy for recording interest and penalties associated with uncertain tax positions is to record such items as a component of tax expense. No material amounts of tax-related interest or penalties were recorded during the years ended December 31, 2019 and 2018. Stock-Based Compensation Stock-based compensation expense for equity instruments issued to employees is measured based on the grant-date fair value of the awards. The fair value of employee stock options and offerings under the 2019 Employee Stock Purchase Plan (the “ESPP”) are estimated on the date of grant using the Black-Scholes option-pricing valuation model. The Company recognizes compensation costs on a straight-line basis for all employee stock-based compensation awards over the requisite service period of the awards. For options, the requisite service period is generally the awards’ vesting period (typically four years ). For the ESPP, the requisite service period is generally the period of time from the offering date to the purchase date. Forfeitures are accounted for as they occur. Deferred Offering Costs Deferred offering costs consist primarily of legal and accounting fees, which are direct and incremental costs related to the IPO. Deferred offering costs of $2,517,000 , along with $5,152,000 in underwriting discounts and commissions, were offset against the gross IPO proceeds of $73,600,000 for the year ended December 31, 2019. As of December 31, 2018 , the Company had incurred $91,000 in deferred offering costs, which are reported as other assets - long-term on the balance sheet. Comprehensive Income (Loss) Comprehensive income (loss) is defined as a change in equity during a period from transactions and other events and circumstances from non-owner sources. The Company’s comprehensive income (loss) was the same as its reported net income (loss) for all periods presented. Accounting Pronouncements Yet to be Adopted In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) (“ASU 2016-02”), which supersedes FASB ASC Topic 840, Leases (Topic 840), and provides principles for the recognition, measurement, presentation and disclosure of leases for both lessees and lessors. The new standard requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the lessee. This classification will determine whether lease expense is recognized based on an effective interest method for finance leases or on a straight-line basis over the term of the lease for operating leases. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than 12 months regardless of classification. Leases with a term of 12 months or less will be accounted for similar to existing guidance for operating leases. For companies that are not emerging growth companies (‘‘EGCs’’), ASU 2016-02 is effective for fiscal years beginning after December 15, 2018. For EGCs, the ASU was to be effective for fiscal years beginning after December 15, 2019. However, in November 2019, the FASB issued ASU 2019-10, Financial Instruments—Credit Losses (Topic 326), Derivatives and Hedging (Topic 815) and Leases (Topic 842): Effective Dates (“ASU 2019-10”), which included a one-year deferral of the effective date of ASU 2016-02 for certain entities. As a result, the ASU is now effective for EGCs for fiscal years beginning after December 15, 2020, and interim periods within fiscal years beginning after December 15, 2021. The Company expects to adopt the new standard in the fourth quarter of 2021 using the modified retrospective method, under which the Company will apply Topic 842 to existing and new leases as of January 1, 2021, but prior periods will not be restated and will continue to be reported under Topic 840 guidance in effect during those periods. The Company anticipates that the adoption will not have a material impact on its statements of operations and comprehensive income (loss) or its statements of cash flows but expects to recognize right-of-use assets and liabilities for lease obligations associated with its operating leases. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments—Credit Losses (“ASU 2016-13”), which requires the measurement of expected credit losses for financial instruments carried at amortized cost, such as accounts receivable, held at the reporting date based on historical experience, current conditions and reasonable forecasts. The main objective of this ASU is to provide financial statement users with more decision-useful information about the expected credit losses on financial instruments and other commitments to extend credit held by a reporting entity at each reporting date. In November 2018, the FASB issued ASU No. 2018-19, Codification Improvements to Topic 326, Financing Instruments—Credit Losses , which included an amendment of the effective date for nonpublic entities. For non-EGCs, ASU 2016-13 is effective for fiscal years beginning after December 15, 2019. For EGCs, the standard was to be effective for fiscal years beginning after December 15, 2021. However, in November 2019, the FASB issued ASU 2019-10, which included a one-year deferral of the effective date of ASU 2016-13 for certain entities. As a result, ASU is now effective for EGCs for fiscal years beginning after December 15, 2022, including interim periods within those fiscal years. The Company does not currently believe the adoption of this standard will have a significant impact on its financial statements, given its history of minimal bad debt expense relating to trade accounts receivable. In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (“ASU 2019-12”), which eliminates certain exceptions to the general principles in Topic 740 and simplifies other areas of the existing guidance. For non-EGCs, ASU 2019-12 is effective for fiscal years beginning after December 15, 2020, and interim periods within those fiscal years. For EGCs, the standard is effective for fiscal years beginning after December 15, 2021, and interim periods within fiscal years beginning after December 15, 2022. Early adoption is permitted. The Company is currently evaluating the impact of ASU 2019-12 on its financial statements.

Earnings (Loss) Per Share

Earnings (Loss) Per Share	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Earnings (Loss) Per Share	Earnings (Loss) Per Share Basic earnings (loss) per share is computed by dividing net income (loss) attributable to common stockholders for the period by the weighted-average number of common shares outstanding during the period. The weighted-average number of common shares outstanding includes shares associated with the July 2019 Warrant (as defined in Note 7), which are deemed to have been issued for purposes of calculating basic and diluted earnings (loss) per share, due to the nominal exercise price. On July 29, 2019, the Company completed the IPO, in which it issued and sold 4,600,000 shares of common stock. Also on that date, all of the Company’s outstanding convertible preferred stock and convertible promissory notes automatically converted into 8,181,992 and 1,661,106 shares, respectively, of common stock and certain outstanding warrants to purchase Series F convertible redeemable preferred stock were net exercised for an aggregate of 27,207 shares of common stock. These shares are included in the Company’s weighted-average number of common shares outstanding starting on that date. Diluted earnings (loss) per share reflects the additional dilution from potential issuances of common stock, such as stock issuable pursuant to the exercise of stock options, as well as from the possible conversion of the Company’s convertible preferred stock, convertible promissory notes and exercise of outstanding warrants. The treasury stock and if-converted methods are used to calculate the potential dilutive effect of these common stock equivalents. However, potentially dilutive shares are excluded from the computation of diluted loss per share when their effect is antidilutive. The following table shows the computation of basic and diluted earnings (loss) per share for the years ended December 31, 2019 and 2018 (in thousands, except per share data): Years Ended December 31, 2019 2018 Numerator: Net income (loss) attributable to common stockholders $ 2,991 $ (10,163 ) Assumed conversion of convertible promissory notes (1) : Subtract: Extinguishment gain (5,213 ) — Add: Interest expense and change in fair value of embedded derivative 420 — Numerator for diluted loss per share $ (1,802 ) $ (10,163 ) Denominator: Weighted-average common shares outstanding, basic 8,584 1,906 Assumed conversion of convertible promissory notes (1) 74 — Weighted-average common shares outstanding, diluted 8,658 1,906 Earnings (loss) per share attributable to common stockholders: Basic $ 0.35 $ (5.33 ) Diluted $ (0.21 ) $ (5.33 ) (1) For the year ended December 31, 2019 , reflects the assumed conversion of the Q1 2019 Notes (as defined in Note 7) into shares of common stock beginning July 1, 2019, in accordance with the requirements in ASC 260, Earnings per Share , for contingently issuable shares due to the contingency not being met until the third quarter of 2019. The July 2019 Note (as defined in Note 7), was excluded from the computation of diluted earnings (loss) per share prior to its conversion on July 29, 2019 in connection with the IPO, as disclosed below. For the year ended December 31, 2019, the computation of diluted loss per share excludes the assumed conversions of the convertible preferred stock, assumed conversion of the July 2019 Note (in each case, for the time prior to their actual conversions), assumed exercise of all stock options, assumed issuance of shares under the ESPP, and the assumed exercise of all common stock warrants because to include them would be antidilutive. Due to the Company reporting a net loss attributable to common stockholders for the year ended December 31, 2018, all potentially dilutive securities are antidilutive and are excluded from the computations of diluted loss per share for those periods. The table below provides the weighted-average number of potential common shares associated with outstanding securities not included in the Company’s calculation of diluted earnings (loss) per share for the years ended December 31, 2019 and 2018 because to do so would be antidilutive (in thousands): Years Ended December 31, 2019 2018 Convertible preferred stock 4,679 7,845 Convertible promissory note (1) 33 — Stock options 1,820 1,429 Common stock warrants 41 — Preferred stock warrants 80 132 Employee stock purchase plan 24 — Total 6,677 9,406 (1) Associated with the July 2019 Note.

Property and Equipment, Net

Property and Equipment, Net	12 Months Ended
	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	Property and Equipment, Net Property and equipment, net consisted of the following (in thousands): As of December 31, 2019 2018 Lab equipment $ 1,563 $ 1,153 Computer equipment 887 629 Leasehold improvements 635 554 Furniture and fixtures 178 102 Total 3,263 2,438 Less accumulated depreciation (1,203 ) (909 ) Property and equipment, net $ 2,060 $ 1,529 Depreciation expense was recorded in the statements of operations and comprehensive income (loss) as follows (in thousands): Years Ended December 31, 2019 2018 Cost of sales $ 277 $ 233 Research and development 7 4 Selling, general and administrative 70 50 Total $ 354 $ 287

Intangible Assets, Net

Intangible Assets, Net	12 Months Ended
	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets, Net	Intangible Assets, Net Intangible assets consist of capitalized license costs as follows (in thousands): As of December 31, 2019 2018 Value Weighted-Average Remaining Life (Years) Value Weighted-Average Remaining Life (Years) Licenses $ 275 0 $ 275 0 Accumulated amortization (275 ) (271 ) Intangible assets, net $ — $ 4 Amortization expense was $4,000 and $36,000 , for the years ended December 31, 2019 and 2018 , respectively.

Other Accrued Liabilities

Other Accrued Liabilities	12 Months Ended
	Dec. 31, 2019
Payables and Accruals [Abstract]
Other Accrued Liabilities	Other Accrued Liabilities Other accrued liabilities consisted of the following (in thousands) : As of December 31, 2019 2018 Accrued state income taxes $ 79 $ 9 Accrued interest 184 185 Accrued royalties 169 240 Accrued service fees 1,162 281 Employee stock purchase plan contributions 218 — Total $ 1,812 $ 715

Convertible Promissory Notes

Convertible Promissory Notes	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Convertible Promissory Notes	Convertible Promissory Notes Q1 2019 Notes In January and February 2019, the Company issued $11,770,000 principal amount of unsecured convertible promissory notes (the “Q1 2019 Notes”), of which $4,756,000 was with related parties (executive officers, members of the Company’s Board of Directors or entities affiliated with them). The Q1 2019 Notes bore simple interest at a rate of 8% per annum. Originally, the Q1 2019 Notes had a maturity date of January 31, 2020, but on July 3, 2019, the Company entered into an amendment with the holders of the Q1 2019 Notes to extend the maturity to June 30, 2020. Such amendment was treated as a modification of the existing debt and therefore no extinguishment gain or loss was recognized in connection with the amendment. Prior to the actual conversion of the Q1 2019 Notes on July 29, 2019 (discussed below), on or before the maturity date, the entire outstanding principal amount of and accrued interest on the Q1 2019 Notes (the “Conversion Amount”), was automatically convertible into shares of the Company’s equity securities issued and sold in a single or series of related transactions, with the principal purpose of raising capital, in which the Company sold shares of such equity securities for aggregate gross proceeds of at least $10.0 million (the “Next Equity Financing”). The number of shares of such equity securities issuable in the Next Equity Financing was equal to the quotient of the Conversion Amount as of the closing date of the Next Equity Financing divided by a per share price that is equal to 80% of the lowest per share purchase price of the equity securities sold in the Next Equity Financing. If the Q1 2019 Notes had not been repaid or converted prior to the maturity date, then, at the request of the holders of a majority of the then-outstanding principal amount of and accrued interest on the Q1 2019 Notes, the Conversion Amount as of the maturity date would have converted into shares of the Company’s Series F redeemable convertible preferred stock, or any senior equity security issued by the Company after the first issuance of the Q1 2019 Notes, in each case at a conversion price equal to the price at which such security was last sold (which was $5.8208 for shares of the Company’s Series F redeemable convertible preferred stock). If a change of control of the Company would have occurred while the Q1 2019 Notes were outstanding, the Company would have been required to repurchase each note from each holder at a repurchase price equal to two times the principal amount of such Note, plus any accrued and unpaid interest on such note as of the date of such repurchase. The Company determined that the Q1 2019 Notes contained embedded derivatives that required bifurcation and separate accounting under ASC 815-15, Embedded Derivatives . The Company determined that two such features in the Q1 2019 Notes were not considered clearly and closely related to the host debt instrument and therefore required separate accounting: (i) the automatic conversion feature in connection with the Next Equity Financing and (ii) the acceleration upon a change of control feature. Under ASC 815-15, these features are bundled together and accounted for as a single, compound embedded derivative. The Company determined the fair value of the embedded derivative liability at the issuance date, creating a discount to the carrying value of the Q1 2019 Notes, which was being amortized over the life of the debt using the effective interest method. The embedded derivative was recorded at fair value each reporting period, with changes in fair value recorded as “other expense, net” in the statements of operations and comprehensive income (loss). No hedge accounting treatment was applied. For details regarding the fair value measurement of the embedded derivative, see Note 10. The Company also assessed the optional conversion feature into Series F redeemable convertible preferred stock at maturity and determined that this feature did not meet the definition of a derivative instrument because the settlement terms involved the gross delivery of the underlying shares, which were not readily convertible to cash. The Company then assessed whether this feature caused the Q1 2019 Notes to be subject to ASC 470-20, Debt with Conversion and Other Options (“ASC 470-20”) , and determined that the beneficial conversion feature guidance was applicable to the Q1 2019 Notes. At issuance, the Company concluded that the Q1 2019 Notes had a beneficial conversion feature because the fair value of the Series F preferred stock exceeded the conversion price of $5.8208 per share that would have been applicable under the optional conversion at maturity, assuming no other equity securities senior to Series F preferred stock were sold. Under ASC 470-20, this beneficial conversion feature was measured at intrinsic value as of the issuance date of the Q1 2019 Notes and was recognized as additional paid-in capital, creating a discount to the carrying value of the Q1 2019 Notes that was being amortized over the life of the debt using the effective interest method. The closing of the IPO on July 29, 2019 was considered to be the Next Equity Financing under the terms of the Q1 2019 Notes. Accordingly, on July 29, 2019, the Conversion Amount of the Q1 2019 Notes as of such date converted into 954,074 shares of common stock based on a price of $12.80 per share, or 80% of the IPO price of $16.00 per share. The conversion of the Q1 2019 Notes was considered an extinguishment for accounting purposes. The Company recognized an extinguishment gain of $5,213,000 in connection with the conversion with extinguishment consideration measured at $15,265,000 , which is calculated as the number of shares issued upon conversion multiplied by the IPO price of $16.00 per share. All of this consideration was allocated to additional paid-in capital to redeem the beneficial conversion feature. The following table summarizes the aggregate values recorded for the Q1 2019 Notes as of their original issuance dates. As noted above, the Q1 2019 Notes were converted into shares of common stock in connection with the closing of the IPO on July 29, 2019 (in thousands) . At Original Issuance (1) Liability component: Principal (including $4,756 with related parties) $ 11,770 Unamortized issuance costs (75 ) Unamortized discount from beneficial conversion feature (8,378 ) Unamortized discount from embedded derivative (2,816 ) Net carrying amount of the liability component $ 501 Embedded derivative liability $ 2,816 Equity Component: Carrying value of beneficial conversion feature recorded in additional paid-in capital $ 8,378 (1) The Q1 2019 Notes were issued on January 31, 2019, February 12, 2019 and February 27, 2019. Amortization of discounts and issuance costs on the Q1 2019 Notes totaled $1,216,000 for the year ended December 31, 2019, and were included in interest expense. The amounts recognized in net income for the year ended December 31, 2019 for the embedded derivative liability are as follows (in thousands) : Gain (Loss) Recognized in Net Income Statement of Operations and Comprehensive Income (Loss) Location Year Ended December 31, 2019 Derivatives Not Classified as Hedging Instruments Embedded derivative in convertible promissory notes Other expense, net $ (237 ) July 2019 Note On July 12, 2019, the Company issued an unsecured convertible promissory note having a principal amount of $10,000,000 (the ‘‘July 2019 Note’’) to an investor. The July 2019 Note bore simple interest at a rate of 8% per annum and had an original maturity date of June 30, 2020. The IPO triggered an automatic conversion feature of the July 2019 Note under which the outstanding principal amount plus accrued interest converted into 707,032 shares of common stock in connection with the closing of the IPO on July 29, 2019, based on a price derived from a valuation calculated pursuant to the terms of the July 2019 Note. In connection with the July 2019 Note issuance, the Company issued the purchaser of the July 2019 Note a warrant to purchase up to 209,243 shares of common stock at an exercise price of approximately $0.001 per share (the “July 2019 Warrant”), as discussed further in Note 13. The Company elected to account for the July 2019 Note under the fair value option in accordance with ASC 825, Financial Instruments. Absent the election of the fair value option, there were several embedded features of the July 2019 Note which would have required separate accounting as an embedded derivative. Given the complexity of these features and the short time period the July 2019 Note was actually outstanding, the Company elected the fair value option to simplify the accounting for the July 2019 Note. Under the fair value option, changes in fair value are recorded in the statements of operations and comprehensive income (loss) each period as “Other expense, net.” The Company received $10,000,000 from the purchaser and incurred $764,000 in issuance costs, resulting in net proceeds of $9,236,000 . The Company subsequently adjusted the fair value of the July 2019 Note to its conversion date fair value of $11,313,000 , which was calculated as the number of common shares into which the July 2019 Note became actually convertible in connection with the IPO multiplied by the IPO price of $16.00 per share. No portion of the change in fair value was deemed to be associated with changes in instrument-specific credit risk, due to the short period of time the July 2019 Note was outstanding. Interest expense and the issuance costs associated with the July 2019 Note were included as part of the change in fair value recorded in “Other expense, net.” Because the initial fair value of the July 2019 Note exceeded the proceeds received, the Company did not allocate any portion of the proceeds to the July 2019 Warrant.

Long-Term Debt

Long-Term Debt	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Long-Term Debt	Long-Term Debt The Company’s long-term debt consists of term debt and a revolving line of credit and are presented in the table below (in thousands): As of December 31, 2019 2018 Term debt $ 26,688 $ 21,350 Revolving line of credit — 5,000 Total principal amount 26,688 26,350 Unamortized discount and issuance costs (1,566 ) (1,850 ) Total long-term debt 25,122 24,500 Less: Current portion of long-term debt (5,833 ) — Total long-term debt, less current portion $ 19,289 $ 24,500 Future maturities of principal amounts on long-term debt as of December 31, 2019 are as follows (in thousands): Years Ending December 31, 2020 $ 5,833 2021 10,000 2022 10,855 2023 — 2024 — Total $ 26,688 Term Debt On November 30, 2018 (the ‘‘Closing Date’’), the Company entered into a new Loan and Security Agreement (the ‘‘2018 LSA’’) with Oxford Finance LLC (‘‘Oxford’’), as collateral agent, and Oxford and Silicon Valley Bank (‘‘SVB’’) as equal syndicated lenders (collectively, the ‘‘Lenders’’). The 2018 LSA replaced the Company’s previous lending arrangement and provided for a $20.0 million secured term loan credit facility (the ‘‘2018 Term Loan’’) and a credit line of up to $5.0 million (discussed in the ‘‘Revolving Line of Credit’’ section below), prior to amendment of the 2018 LSA on June 13, 2019, as discussed below. The Company’s obligations under the 2018 LSA are secured by substantially all of its assets, excluding intellectual property and subject to certain other exceptions and limitations. The Company has the right to prepay the 2018 Term Loan in whole or in part at any time, subject to a prepayment fee of 1.50% prior to November 30, 2020 and 0.75% thereafter. Upon prepayment, the Company is also obligated to pay a non-refundable early termination fee of $497,000 . Amounts prepaid or repaid under the 2018 Term Loan may not be reborrowed. Initially, the 2018 LSA contained a financial covenant that required the Company to achieve a monthly trailing six-month revenue target each month throughout the term of the agreement, but the covenant was amended on June 13, 2019 and changed to a monthly trailing three-month target, as discussed further below. As of December 31, 2019 and December 31, 2018, the Company was in compliance with this covenant. On June 13, 2019, the Company entered into an amendment to the 2018 LSA (the “First Amendment”), which, among other things, (i) eliminated the $5.0 million revolving line and increased the 2018 Term Loan by $5.0 million and (ii) amended the financial covenant to require the Company to achieve a monthly trailing three-month revenue target each month throughout the term of the agreement. The revenue targets were amended primarily to align with a more current reflection of the Company’s revenue projections after taking into account the impact of ASC 606 on the Company’s revenue recognition following the Company’s early adoption of ASC 606. The First Amendment was accounted for as a modification of the 2018 LSA, and therefore no extinguishment gain or loss was recognized. For each month through December 31, 2019, the trailing three-month revenue requirements were calculated as a percentage of the Company’s previously approved applicable monthly revenue projections. In February 2020, the Company entered into an amendment of the 2018 LSA (the “Second Amendment”) that, among other things, changed the covenant from being tested monthly to quarterly testing. In March 2020, the Company entered into an amendment of the 2018 LSA (the “Third Amendment”) with the Lenders to establish revenue targets for the year ending December 31, 2020. For quarterly periods ending after December 31, 2020, the trailing three-month revenue requirements will be determined by the Lenders upon receipt and review of the Company’s quarterly financial projections for the year, subject to certain specified criteria regarding minimum requirements. Revenues, if any, that the Company recognizes as a result of an ALJ appeal process from consolidated claims initiatives for DecisionDx-Melanoma do not count toward the minimum revenue requirements. In addition, the 2018 LSA contains customary conditions of borrowing, events of default and covenants, including covenants that restrict the Company’s ability to dispose of assets, merge with or acquire other entities, incur indebtedness and make distributions to holders of the Company’s capital stock. Should an event of default occur, including the occurrence of a material adverse change, the Company could be liable for immediate repayment of all obligations under the 2018 LSA. The Second Amendment included a waiver, by the Lenders, of an event of default of the Company attributable to maintaining a balance in a certain third-party deposit account, beyond the maximum level permitted, without obtaining a control agreement for such deposit account in favor of the collateral agent, Oxford. In addition to the waiver, the Second Amendment also provided a modification to increase the maximum balance permitted for this deposit account. The Company is currently in compliance with this provision of the 2018 LSA. Should the Company seek to further amend the terms of the 2018 LSA, the consent of Oxford and SVB would be required. The 2018 Term Loan bears interest at a floating rate equal to the greater of (1) 8.55% and (2) the 30-day U.S. LIBOR rate as reported in the Wall Street Journal on the last business day of the month that precedes the month in which the interest will accrue, plus 6.48% . The applicable interest rate on the 2018 Term Loan was 8.55% and 8.98% at December 31, 2019 and December 31, 2018 , respectively. Interest on the 2018 Term Loan is payable monthly in arrears. The Company is permitted to make interest-only payments on the 2018 Term Loan for the 18 months following the Closing Date. The principal is required to be repaid in 30 equal monthly installments beginning on June 1, 2020. All unpaid principal and accrued and unpaid interest are due on November 1, 2022 (the “2018 Term Loan Maturity Date”). The Company is also obligated to make an additional final payment of 6.75% of the aggregate original principal amount, or $1,687,500 as of December 31, 2019 , upon any prepayment or on the 2018 Term Loan Maturity Date. The final payment amount is being amortized as additional interest expense using the effective interest method over the term of the debt. The 2018 Term Loan was fully funded on the Closing Date and the 2018 Revolving Line (defined and discussed below) was fully drawn upon on the Closing Date. Proceeds from the 2018 LSA were used to repay all outstanding obligations under the Company’s previous lending arrangement and to provide working capital. As a condition of the loan, the Company issued Series F preferred stock warrants to the Lenders with an aggregate initial fair value of $158,000 . In accordance with ASC 480-10, Distinguishing Liabilities from Equity (“ASC 480-10”), the warrants were liability-classified as the underlying to the warrant was a puttable security. The initial recognition of the warrant liability created a discount to the debt, which is being amortized over the debt term using the effective interest method. The 2018 LSA was accounted for as a modification of the previous lending arrangement with SVB and Oxford, and therefore no extinguishment gain or loss was recognized. Revolving Line of Credit Under the 2018 LSA, the Company had a $5.0 million revolving line of credit (the ‘‘2018 Revolving Line’’), contingent on the Company’s satisfaction of borrowing base eligibility requirements. The 2018 Revolving Line bore interest at a floating per annum rate equal to the greater of (1) 6.25% and (2) 5.48% above the U.S. LIBOR rate. The applicable interest rate on the 2018 Revolving Line December 31, 2018 was 7.98% . The 2018 Revolving Line was to be due in full no later than November 30, 2020, but was eliminated in connection with the First Amendment, as discussed above.

Operating Leases

Operating Leases	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Operating Leases	Operating Leases Friendswood Leases The Company leases its office headquarters in Friendswood, Texas (the “820 Friendswood Lease”). As of December 31, 2019, the Company’s commitment under the 820 Friendswood Lease extends through June 30, 2020 and the Company has a one-year renewal option thereafter. If this option is exercised, the term of the 820 Friendswood Lease would extend through June 30, 2021. In December 2019, the Company entered into an agreement to lease new office space in Friendswood, Texas (the “550 Friendswood Lease”) with the intent to replace the 820 Friendswood Lease office space. The 550 Friendswood Lease is expected to commence on or prior to August 1, 2020 and has a 60 -month term, with an option to renew for one additional five-year period. Phoenix Leases In April 2016, the Company took occupancy of a newly constructed office and laboratory facility located in Phoenix, Arizona (the “3737 Phoenix Lease”), replacing its previous facility. On December 16, 2019, the Company entered into an amendment to the 3737 Phoenix Lease and extended the term by 48 months , such that the expiration date is now July 31, 2027. Additionally, the amendment provides the Company with options to extend the term of the 3737 Phoenix Lease for two additional renewal periods of five years each. On December 16, 2019, the Company entered into a lease (the “3707 Phoenix Lease”) of certain additional office space, in Phoenix, Arizona that the Company intends to use such space for clinical and research laboratory purposes as well as general office use. The 3707 Phoenix Lease commenced in January 2020 and has an initial term of 91 months , or through approximately July 31, 2027. The 3707 Phoenix Lease provides the Company with options to extend the initial term for two additional renewal periods of five years each. Other leasing arrangements include office copiers and a corporate apartment. All leases have been classified as operating leases. Rent expense is recognized on a straight-line basis over the term of the leases. Future non-cancellable commitments under all operating leases are as follows (in thousands): Years Ending December 31, 2020 $ 754 2021 995 2022 993 2023 1,029 2024 999 Thereafter 1,625 $ 6,395 Rent expense was $395,000 and $315,000 for the years ended December 31, 2019 and 2018, respectively.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market in an orderly transaction between market participants at the measurement date. The fair value hierarchy prioritizes the inputs to valuation techniques used in measuring fair value. There are three levels to the fair value hierarchy based on the reliability of inputs, as follows: Level 1 – Observable inputs that reflect quoted prices (unadjusted) for identical assets or liabilities in active markets. Level 2 – Inputs other than quoted prices included in Level 1 that are observable for the asset or liability, either directly or indirectly. Level 3 – Unobservable inputs in which little or no market data exists, therefore requiring the Company to develop its own assumptions. Financial instruments measured at fair value are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires management to make judgments and consider factors specific to the asset or liability. The use of different assumptions and/or estimation methodologies may have a material effect on estimated fair values. Accordingly, the fair value estimates disclosed, or amounts recorded may not be indicative of the amount that the Company or holders of the instruments could realize in a current market exchange. The table below provides information (in thousands), by level within the fair value hierarchy, of the Company’s financial assets and liabilities that are accounted for at fair value on a recurring basis as of December 31, 2018 . There were no financial assets and liabilities accounted for at fair value on a recurring basis as of December 31, 2019 . As of December 31, 2018 Quoted Prices in Active Markets for Identical Items (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Liabilities: Preferred stock warrants $ — $ — $ 1,194 $ 1,194 The following table discloses the summary of changes in the fair value of the Level 3 fair value measurements (in thousands): Preferred stock warrant liability Embedded derivative liability in the Q1 2019 Notes The July 2019 Note Balance, January 1, 2018 $ 525 $ — $ — Issuance of warrants 632 — — Change in fair value included in net loss 272 — — Exercised warrants (235 ) — — Balance, December 31, 2018 $ 1,194 $ — $ — Issuance of convertible promissory notes — 2,816 9,236 Change in fair value included in net income 619 237 2,077 Extinguishment of convertible promissory notes and exercise of warrants (68 ) (3,053 ) (11,313 ) Reclassification of preferred stock warrant liability to stockholders’ equity (1,745 ) — — Balance, December 31, 2019 $ — $ — $ — The changes in fair value of the preferred stock warrant liability, the embedded derivative liability and the July 2019 Note were recorded as ‘‘Other expense, net’’ in the statements of operations and comprehensive income (loss). The fair value of the warrants to purchase shares of Series A, Series B, Series E-1, Series E-2, Series E-2A, Series E-3, and Series F redeemable convertible preferred stock was estimated by management using the Black-Scholes option pricing model with the following assumptions: December 31, 2018 Average expected life (years) 9 Expected stock price volatility 64% Risk-free interest rate 2.51% - 2.69% Dividend yield —% In connection with the IPO, all outstanding preferred stock warrants became exercisable for shares of common stock. The Company recorded a final fair value adjustment on the preferred stock warrant liability as of immediately prior to the closing of the IPO based on the IPO price of $16.00 per share. The preferred stock warrant liability was then reclassified to stockholders’ equity and is no longer recorded at fair value on a recurring basis. Certain features of the Q1 2019 Notes were determined to be an embedded derivative requiring bifurcation and separate accounting, as discussed in Note 7. The fair value of the embedded derivative was determined based on a probability-weighted income approach discounted at an interest rate that is consistent with the appropriate market interest rate (ranging from 8.93% to 11.40% ) considering management’s estimates of the probability of the possible settlement outcomes. At inception of the Q1 2019 Notes, management assessed the probability of the occurrence of the Next Equity Financing at 90% . The final fair value adjustment was based upon the actual settlement of the Q1 2019 Notes in connection with the IPO. The Company elected the fair value option for the July 2019 Note, as discussed in Note 7. The change in fair value recorded for the July 2019 Note represents the difference between the net proceeds received and the fair value of the shares issued upon conversion of the July 2019 Note in connection with the IPO, valued at the IPO price of $16.00 per share.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies From time to time, the Company may be involved in legal proceedings arising in the ordinary course of business. The Company believes there is no threatened litigation or litigation pending that could have, individually or in the aggregate, a material adverse effect on the Company’s financial position, results of operations or cash flows.

Convertible Preferred Stock and

Convertible Preferred Stock and Preferred Stock Warrants	12 Months Ended
	Dec. 31, 2019
Stockholders' Equity And Temporary Equity [Abstract]
Convertible Preferred Stock and Preferred Stock Warrants	Convertible Preferred Stock and Preferred Stock Warrants Convertible Preferred Stock As discussed further below, in connection with the IPO, on July 29, 2019, all outstanding shares of convertible preferred stock automatically converted into shares of common stock at a rate of one common share for each 1.219 shares of convertible preferred stock. The Company’s convertible preferred stock was classified outside of stockholders’ equity in accordance with authoritative guidance for the classification and measurement of potentially redeemable securities. The preferred stock was contingently redeemable upon events that are outside of the Company’s control including liquidation, sale, or transfer of control of the Company. The Company had determined not to adjust the carrying values of the convertible preferred stock to liquidation preferences of such shares because of the uncertainty of whether or when such events would occur. Further, except for Series C preferred stock, the preferred stock was redeemable upon the majority vote of specified holders of the preferred stock. Information on liquidation and redemption terms applicable prior to the IPO are discussed further under Liquidation Provisions and Redemption Rights , respectively, below. On January 12, 2018, the Company issued 940,605 shares of Series F redeemable convertible preferred stock in exchange for $5.475 million in cash. In two subsequent closings on May 31, 2018 and June 8, 2018, the Company issued 783,248 and 85,711 additional shares, respectively, in exchange for $4,599,000 and $499,000 , respectively, in cash. The designations, rights and preferences that were associated with the Series F redeemable convertible preferred stock prior to the IPO are provided below. Proceeds of $94,000 from the sale of 16,127 of these shares were received in 2017 prior to issuance. These proceeds were initially recorded as a liability, but in in 2018 these proceeds were reclassified to convertible preferred stock when the shares were ultimately issued. In conjunction with the January 12, 2018 issuance of the Series F redeemable convertible preferred shares, the Company also issued warrants to purchase 67,233 additional shares of redeemable convertible preferred stock at $0.01 per share with an initial fair value of $473,000 . As a result of a 1-for-1.219 reverse stock split effected on July 11, 2019, the conversion price for each series of preferred stock was adjusted to be the original issue price multiplied by 1.219 . Immediately prior to the closing of the IPO, 9,973,884 shares of outstanding convertible preferred stock were automatically converted into 8,181,992 shares of common stock. In connection with the conversion, the Company derecognized the convertible preferred stock at their carrying values and allocated such amounts to common stock and additional paid-in capital effective July 29, 2019. Convertible preferred stock consisted of the following (in thousands, except share and per share data): Convertible preferred stock As of December 31, 2018 Shares Authorized Shares Issued and Outstanding Original Issue Price per Share Original Issue Value Accumulated and Undeclared Dividends Aggregate Liquidation Preference Carrying Value Series C 503,056 503,056 $3.4800 $ 1,751 $ 667 $ 2,417 $ 1,501 Redeemable convertible preferred stock As of December 31, 2018 Shares Authorized Shares Issued and Outstanding Original Issue Price per Share Original Issue Value Accumulated and Undeclared Dividends Aggregate Liquidation Preference Carrying Value Series A 533,711 533,711 $2.1400 $ 1,142 $ 713 $ 1,856 $ 1,142 Series B 816,654 816,654 $2.2500 1,837 983 2,820 1,932 Series D 756,416 756,416 $3.7700 2,852 1,340 4,191 2,852 Series E-1 842,641 829,642 $3.7700 3,128 1,095 4,223 3,099 Series E-2 949,725 934,433 $4.5776 4,277 1,503 5,780 4,277 Series E-2A 27,306 27,306 $4.5776 125 39 164 125 Series E-3 830,554 824,000 $5.3405 4,401 1,364 5,764 4,394 Series F 4,883,486 4,734,613 $5.8208 27,559 5,212 32,772 27,174 Total 9,640,493 9,456,775 $ 45,321 $ 12,249 $ 57,570 $ 44,995 Any discount to the original issue price was being accreted with a charge to additional paid-in capital over the period through the earliest date the redeemable convertible preferred stock could become redeemable. See the Redemption Rights section below for additional information. Unpaid cumulative accruing dividends were included in calculating the aggregate liquidation preference, but such dividends were not recorded in the financial statements since a liquidation event or a deemed liquidation did not become probable of occurring. See the Liquidation Provisions section below for additional information. The rights, preferences and privileges of the Series A, Series B, Series C, Series D, Series E-1, Series E-2, Series E-2A, Series E-3, and Series F convertible preferred stock that existed prior to the IPO are as follows: Dividends The holders of the outstanding shares of Series A, Series B, Series C, Series D, Series E-1, Series E-2, Series E-2A, Series E-3, and Series F convertible preferred stock were entitled to receive, when and if declared by the Board of Directors, a cash dividend in the following order of preference and at the rates per annum noted: Convertible Preferred Stock Class Annual Dividend Rate Series F $ 0.46570 Series E-3 $ 0.42720 Series E-2A $ 0.36620 Series E-2 $ 0.36620 Series E-1 $ 0.30160 Series D $ 0.30160 Series C $ 0.27840 Series B $ 0.18000 Series A $ 0.17120 The right to receive dividends on shares of convertible preferred stock was not cumulative, and no right to such dividends accrued to holders of convertible preferred stock by reason of the fact that dividends on said shares were not declared or paid in any calendar year. However, refer to Liquidation Provisions below for information regarding cumulative dividends that would have been payable upon a liquidation event or a deemed liquidation event. Conversion Rights Each share of Series A, Series B, Series C, Series D, Series E-1, Series E-2, Series E-2A, Series E-3, and Series F convertible preferred stock was, at the option of the holder, convertible at any time into that number of fully paid and non-assessable shares of common stock determined by dividing the original issue price by the conversion price. The conversion price for each series of convertible preferred stock was initially the original issue price of such series of convertible preferred stock and was subject to adjustment in accordance with the conversion provisions contained in the Company’s Amended and Restated Certificate of Incorporation. As a result of a 1-for-1.219 reverse stock split effected on July 11, 2019, the conversion price for each series of convertible preferred stock was the original issue price multiplied by 1.219 . Each share of convertible preferred stock could have been automatically be converted into shares of common stock based on the then effective conversion price (i) upon the affirmative election of the holders of at least a majority of the outstanding shares of Series E-1, Series E-2, Series E-2A, Series E-3, and Series F convertible preferred stock or (ii) immediately upon the closing of a firmly underwritten public offering filed under the Securities Act of 1933, as amended, covering the offer and sale of common stock for the account of the Company in which the gross cash proceeds to the Company are at least $30 million . The closing of the Company’s IPO satisfied the conditions for an automatic conversion of the shares of convertible preferred stock into shares of common stock. Liquidation Provisions Upon a liquidation event (any liquidation, dissolution or winding up on the Company, whether voluntary or involuntary) or a deemed liquidation event (generally, a change of control of the Company or the sale of substantially all the assets or intellectual property of the Company), the holders of Series A, Series B, Series C, Series D, Series E-1, Series E-2, Series E-2A, Series E-3, and Series F convertible preferred stock would have been entitled to distributions based on the liquidation value of the stock, which was initially set equal to the original issue price for the series of convertible preferred stock, plus any unpaid cumulative accruing dividends, at the annual dividend rates provided above, accruing from the date of issuance of the shares of convertible preferred stock, plus any other declared and unpaid dividends. Regarding liquidation preferences, the holders of each successive series of preferred stock would have been entitled to receive on a pari passu basis and prior and in preference to any distribution of any of the assets or surplus funds of the Company to the holders of any prior-issued preferred stock, or common stock, the liquidation preference specified for each share of preferred stock. Voting Rights Each holder of convertible preferred stock was entitled to the number of votes equal to the number of shares of common stock into which the shares of convertible preferred stock could have been converted. Holders of the convertible preferred stock were entitled to vote on all matters on which the holders of common stock were entitled to vote. Redemption Rights The holders of at least a majority (voting together as a single class and not as a separate series, and on an as-converted basis) of the then-outstanding shares of Series A preferred stock, Series B preferred stock, Series D preferred stock, Series E-1 preferred stock, Series E-2 preferred stock, Series E-2A preferred stock, Series E-3 preferred stock and Series F preferred stock (the “Redemption Stock”), and the holders of at least a majority (voting together as a single class and not as a separate series, and on an as-converted basis) of the then-outstanding shares of Series E-1 preferred stock, Series E-2 preferred stock, Series E-2A preferred stock, Series E-3 preferred stock and Series F preferred stock could have requested, in writing, and any time after five years from the date of first issuance of Series F preferred stock (i.e., five years from July 15, 2015), the redemption of all outstanding shares of the Redemption Stock. However, on July 10, 2019, the earliest redemption date was effectively changed to July 15, 2025, in connection with an amendment to the Company’s Amended and Restated Certificate of Incorporation. The Company, upon such written request, would have been required to redeem all outstanding shares in three equal annual installments beginning on the date specified in the redemption request, which date could not have been less than 90 days after the Company’s receipt of such request. The redemption price would have been the original issue price of the preferred stock plus an amount for all declared and unpaid dividends thereon. Preferred Stock Warrant Liabilities The Company previously issued warrants to purchase shares of its convertible preferred stock. The warrant provided the holder the option to purchase a specified number of shares of a particular series of the Company’s convertible preferred stock for a specified price. The holder may exercise the warrant in cash or exercise pursuant to a cashless exercise whereby a calculated number of shares are withheld upon exercise to satisfy the exercise price. The warrants do not provide the holder any voting rights until the warrants are exercised. In accordance with their terms, in connection with the IPO, all outstanding warrants to purchase shares of convertible preferred stock became exercisable for shares of common stock at a rate of one common stock warrant for every 1.219 preferred stock warrants. Exercise prices of the warrants were also adjusted upon conversion by multiplying each of the exercise prices by 1.219 . Immediately prior to the closing of the IPO, certain outstanding warrants to purchase shares of Series F convertible redeemable preferred stock were net exercised for an aggregate of 27,207 shares of common stock. In accordance with ASC 480-10, the Company accounted for preferred stock warrants outstanding as a liability at fair value and adjusted the instruments to fair value at each reporting period. This liability was subject to re-measurement at each balance sheet date until exercised, and any change in fair value was recognized in the Company’s statements of operations and comprehensive loss as other income (expense), net. The fair value of the warrants issued by the Company was estimated using a Black-Scholes model at each measurement date. Refer to Note 10 for additional information on the fair value measurement assumptions and changes in the fair value of the preferred stock warrants recorded on the Company’s balance sheets. Warrants to purchase redeemable convertible preferred shares consisted of the following: As of December 31, 2018 Warrants Year of First Issuance Shares Exercise Price Year of Expiration Exercised Expired Outstanding Series A Preferred Stock 2008 108,057 $2.1400 2015 (96,375 ) (11,682 ) — Series B Preferred Stock 2010 86,667 $2.2500 2017 (86,667 ) — — Series E-1 Preferred Stock 2014 16,249 $3.7700 2024 (3,250 ) — 12,999 Series E-2 Preferred Stock 2014 15,292 $4.5776 2024 — — 15,292 Series E-3 Preferred Stock 2015 6,554 $5.3405 2024 — — 6,554 Series F Preferred Stock 2016 103,090 $5.8208 2026-2028 — — 103,090 Series F Preferred Stock 2018 67,233 $0.0100 2023 (32,951 ) — 34,282 Total 403,142 (219,243 ) (11,682 ) 172,217 In connection with the preferred stock warrants becoming exercisable for common stock, the Company reclassified the preferred stock warrant liability balance to additional paid-in capital effective July 29, 2019 due to meeting the criteria under U.S. GAAP for classification in stockholders’ equity. See Note 13 for information on outstanding common stock warrants at December 31, 2019 .

Stockholders' Equity (Deficit)

Stockholders' Equity (Deficit)	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Stockholders' Equity (Deficit)	Stockholders’ Equity (Deficit) Common Stock The Company’s Amended and Restated Certificate of Incorporation, dated July 29, 2019, authorizes the Company to issue up to 200,000,000 shares of common stock with a par value of $0.001 per share. The holders of common stock shall have one vote for each share. The Company is also authorized to issue up to 10,000,000 shares of preferred stock with a par value of $0.001 per share. The preferred stock may be issued from time to time in one or more series, with rights, preferences, limitations and restrictions as determined by the Company’s Board of Directors. No dividends were declared or paid during the years ended December 31, 2019 or 2018. The terms of the 2018 LSA restrict the Company’s ability to pay dividends on common stock without prior consent of the Lenders. On July 11, 2019, the Company effected a 1-for-1.219 reverse stock split of its common stock. The par value and the authorized number of shares of the common stock were not affected by the reverse stock split. The reverse stock split resulted in an adjustment to the Series A, B, C, D, E-1, E-2, E-2A, E-3, and F preferred stock conversion prices to reflect a proportional decrease in the number of shares of common stock to be issued upon conversion. The accompanying financial statements and notes to the financial statements give retroactive effect to the reverse stock split for all periods presented. In connection with the issuance of the July 2019 Note, the Company issued the purchaser of the July 2019 Note a warrant to purchase up to 209,243 shares of common stock at an exercise price of approximately $0.001 per share. The July 2019 Warrant, which expires on July 12, 2026, was initially exercisable for 50% of the shares subject to the warrant and became exercisable for the remaining 50% of the shares subject to the warrant upon the holder’s satisfaction of a requirement to purchase a certain amount of equity securities of the Company. The holder satisfied such requirement on July 29, 2019 in connection with a purchase of common stock in the IPO. On July 29, 2019, the Company completed the initial public offering of its common stock. In connection with the IPO, the Company issued and sold 4,600,000 shares of its common stock, including 600,000 shares associated with the full exercise of the underwriters’ option to purchase additional shares, at a price to the public of $16.00 per share. The Company received approximately $65.9 million in net proceeds from the IPO, after deducting underwriting discounts and commissions and other offering expenses payable by the Company. Common Stock Warrants Information about common stock warrants outstanding as of December 31, 2019 is presented in the table below: As of December 31, 2019 Expiration date Number of shares Exercise price July 12, 2026 209,243 $ 0.001 March 31, 2027 26,428 $ 7.10 November 30, 2028 8,809 $ 7.10 Total 244,480 The common stock warrants are classified as stockholders’ equity and no adjustments are recorded for changes in fair value. There were no common stock warrants outstanding as of December 31, 2018 .

Stock Incentive Plans and Stock

Stock Incentive Plans and Stock Based Compensation	12 Months Ended
	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
Stock Incentive Plans and Stock Based Compensation	Stock Incentive Plans and Stock Based Compensation Stock Incentive Plans The Company’s stock incentive plans provide for the granting of options to purchase common stock and other equity-based awards to employees, directors and consultants of the Company. On September 6, 2008, the Company adopted the 2008 Stock Plan (the “2008 Plan”), on August 15, 2018, the Company adopted the 2018 Stock Plan (the “2018 Plan”) and on July 24, 2019, the Company adopted the 2019 Equity Incentive Plan (the “2019 Plan”). Following the adoption of the 2018 Plan, no additional stock awards were granted under the 2008 Plan and following the adoption of the 2019 Plan, no additional stock awards were granted under the 2018 Plan. Options under the plans may be granted as incentive stock options (“ISOs”) or non-statutory stock options (“NSOs”). ISOs may only be granted to Company employees (including directors who are also considered employees). NSOs may be granted to Company employees, directors and consultants. Options may be granted for terms up to ten years from the date of grant, as determined by the Board of Directors; provided, however, that with respect to an ISO granted to a person who owns stock representing more than 10% of the voting power of all classes of stock of the Company, the terms shall be for no more than five years from the date of grant. The exercise price of options granted must be no less than 100% of the fair market value of the shares on the date of grant, provided, however, that with respect to an ISO granted to an employee who at the time of grant of such options owns stock representing more than 10% of the voting power of all classes of stock of the Company, the exercise price shall not be less than 110% of the fair market value of the shares on the date of grant. Options generally vest over four years (generally 25% after one year and monthly thereafter), subject to the option holder’s continued service with the Company. The Company issues new shares to satisfy option exercises. Activity under the Company’s stock plans for the years ended December 31, 2019 and 2018 is set forth below: Weighted-Average Shares Available for Grant Stock Options Outstanding Exercise Price Remaining Contractual Term (Years) Aggregate Intrinsic Value (in thousands) Balance as of December 31, 2017 551,918 1,175,987 $ 1.79 Additional options authorized 410,172 — — Granted (580,402 ) 580,402 2.39 Exercised — (19,755 ) 1.91 Forfeited/Cancelled 77,038 (77,038 ) 1.82 Balance as of December 31, 2018 458,726 1,659,596 $ 1.99 Additional options authorized 2,075,898 — — Granted (1,711,325 ) 1,711,325 19.41 Exercised — (693,127 ) 1.70 Forfeited/Cancelled 39,828 (39,828 ) 6.36 Balance as of December 31, 2019 863,127 2,637,966 $ 13.30 8.64 $ 55,578 Exercisable at December 31, 2019 (1 ) 590,104 $ 2.20 6.11 $ 18,984 (1) Vested and exercisable options. Additionally, outstanding unvested options to purchase an aggregate of 126,044 shares of common stock with a weighted-average exercise price of $2.39 per share may be exercised prior to vesting as of December 31, 2019 under early-exercise provisions. In the event of such exercise, the shares obtained upon exercise would be restricted and subject to forfeiture prior to vesting. No such early exercises have occurred as of December 31, 2019 . On July 11, 2019, the Company’s Board of Directors approved an increase of 144,878 in the number of shares authorized for issuance under the 2018 Plan. On July 24, 2019, the 2019 Plan became effective. The 2019 Plan authorized 1,931,020 new shares plus the number of shares (not to exceed 1,976,756 shares) that remained available under the 2018 Stock Plan at the time the 2019 Plan became effective and any shares underlying outstanding stock awards granted under the 2018 Plan and 2008 Stock Plan that expire or are repurchased, forfeited, cancelled or withheld. The 2019 Plan also provides for certain automatic increases in the number of shares of common stock reserved for issuance, which resulted in an additional 856,545 shares becoming available effective January 1, 2020. Employee Stock Purchase Plan The ESPP became effective July 24, 2019. Under the ESPP, 411,935 shares of common stock are reserved for future issuance. The ESPP also provides for certain automatic increases in the number of shares of common stock reserved for issuance, which resulted in an additional 171,309 shares becoming available under the ESPP effective January 1, 2020. The Company commenced a series of offerings under the ESPP on October 1, 2019. The initial offering began October 1, 2019, ends on August 31, 2021 (unless terminated earlier, as described below) and consists of four purchase periods. The purchase periods end on the last trading day of February and August 31 of each year. Eligible employees who enroll in the initial offering or any subsequent offering will be able to purchase shares of the Company’s common stock at a discount through payroll deductions, subject to certain limitations. The purchase price of the shares of common stock will be the lesser of (i) 85% of the fair market value of such shares on the offering date and (ii) 85% of the fair market value of such shares on the purchase date. Following the commencement of the initial offering, a new 24 -month offering with four six-month purchase periods will automatically begin approximately every six months thereafter over the term of the ESPP. Offerings will be concurrent, but in the event the fair market value of a share of common stock on the first day of any purchase period during an offering (the “New Offering”) is less than or equal to the fair market value of a share of common stock on the offering date for an ongoing offering (the “Ongoing Offering”), then the Ongoing Offering terminates immediately following the purchase of shares on the purchase date immediately preceding the New Offering and the participants in the terminated Ongoing Offering are automatically enrolled in the New Offering. Notwithstanding the above, the Company’s Board of Directors (or an authorized committee thereof) may modify the terms of or suspend any future offerings prior to their commencement. The Company issues new shares for purchases of stock made pursuant to the ESPP. Determining Fair Value - Summary of Assumptions The Company uses the Black-Scholes option pricing model to estimate the fair value of each option grant or ESPP offering on the date of grant or any other measurement date. Following is a description of the significant assumptions used in the option pricing model: • Expected term . The expected term is the period of time that granted options are expected to be outstanding. For stock options, the Company has set the expected term using the simplified method based on the weighted average of both the period to vesting and the period to maturity for each option, as the Company has concluded that its stock option exercise history does not provide a reasonable basis upon which to estimate the expected term. For the ESPP, the expected term is the period of time from the offering date to the purchase date. • Expected volatility . Because of the limited period of time the Company’s stock has been traded in an active market, the Company calculates volatility by using the historical stock price volatility of a group of similar companies looking back over the estimated life of the option or the ESPP purchase right and averaging the volatilities of these companies. • Risk-free interest rate . The Company bases the risk-free interest rate used in the Black-Scholes valuation model on the market yield in effect at the time of option grant and at the offering date for the ESPP, provided from the Federal Reserve Board’s Statistical Releases and historical publications from the Treasury constant maturities rates for the equivalent remaining terms. • Dividend yield . The Company has not paid, and does not have plans to pay, cash dividends. Therefore, the Company use an expected dividend yield of zero in the Black-Scholes option valuation model. The fair value of the Company’s common stock is also an assumption used to determine the fair value of stock options. Prior to the IPO, our common stock was not publicly traded, therefore the Company estimated the fair value of its common stock. Following the IPO, the fair value of the Company’s common stock is the closing selling price per share of its common stock as reported on the Nasdaq Global Market on the date of grant or other relevant determination date. The Company uses the Black-Scholes option pricing model to estimate the fair value of each option grant on the date of grant or any other measurement date. The following table sets forth the assumptions used to determine the fair value of stock options: Years Ended December 31, 2019 2018 Average expected term (years) 6 6 Expected stock price volatility 56.74% - 60.17% 57.77% - 58.29% Risk-free interest rate 1.63% - 2.47% 2.77% - 3.13% Dividend yield —% —% The following table sets forth assumptions used to determine the fair value of the purchase rights issued under the ESPP: Years Ended December 31, 2019 2018 Average expected term (years) 1.2 Not applicable Expected stock price volatility 61.12% - 68.89% Not applicable Risk-free interest rate 1.56% - 1.80% Not applicable Dividend yield —% Not applicable Stock-Based Compensation Expense Stock-based compensation expense related to stock options and the ESPP is included in the statements of operations and comprehensive income (loss) as follows (in thousands): Years Ended December 31, 2019 2018 Cost of sales $ 170 $ 24 Research and development 165 56 Selling, general and administrative 914 214 Total stock-based compensation expense $ 1,249 $ 294 For the years ended December 31, 2019 and 2018, the weighted-average grant date fair value of options was $10.89 and $1.35 per option, respectively, and the weighted-average grant date fair value for the ESPP granted was $7.32 and nil , respectively. As of December 31, 2019 , the total unrecognized compensation cost related to stock options and the ESPP was $18,417,000 and $678,000 , respectively, which is expected to be recognized on a straight-line basis over a weighted-average period of 3.4 years and 1.6 years, respectively. The total unrecognized compensation costs will be adjusted for forfeitures in future periods as they occur. The intrinsic value of stock options exercised during the year ended December 31, 2019 was $5,151,000 and was no t material for the year ended December 31, 2018 . No tax benefits related to stock-based compensation were recorded in the statements of operations and comprehensive income (loss) during the years ended December 31, 2019 and 2018 due to the valuation allowance on net deferred tax assets.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The components of income tax expense are as follows (in thousands): Years Ended December 31, 2019 2018 Current tax expense U.S. Federal $ — $ — State and local 72 9 Total current 72 9 Deferred tax expense U.S. Federal — — State and local — — Total deferred — — Total income tax expense $ 72 $ 9 The differences between income taxes expected at the U.S. federal statutory rate (21%) and the reported income tax expense are summarized as follows (in thousands): Years Ended December 31, 2019 2018 Pre-tax income (loss) $ 5,349 $ (6,358 ) U.S. federal taxes at statutory rate 1,123 (1,335 ) State income taxes 958 (1,174 ) Mark-to-market losses 566 57 Non-deductible meals 224 119 Convertible debt interest 95 — Research and development (“R&D”) tax credit (251 ) — Change in valuation allowance (2,747 ) 2,278 Stock-based compensation 65 53 Other 39 11 Total income tax expense $ 72 $ 9 Significant components of deferred tax assets and liabilities are as follows (in thousands): As of December 31, 2019 2018 Deferred tax assets: Net operating loss (“NOL”) carryforwards $ 14,077 $ 16,184 Accounts payable 456 390 Accrued liabilities 1,817 1,432 R&D tax credit 993 715 Intangible assets 50 61 Stock-based compensation 127 12 Charitable contributions 2 4 Total deferred tax assets 17,522 18,798 Less valuation allowance (12,420 ) (14,375 ) Deferred tax assets, net $ 5,102 $ 4,423 Deferred tax liabilities: Accounts receivable $ (3,796 ) $ (3,249 ) Prepaid expenses (757 ) (378 ) Property and equipment (246 ) (131 ) Section 481(a) adjustment (cash to accrual) (303 ) (665 ) Total deferred tax liabilities (5,102 ) (4,423 ) Net deferred tax asset (liability) $ — $ — At December 31, 2019, the Company had NOL carryforwards for federal income tax purposes of approximately $57,429,000 of which $43,536,000 will begin to expire in 2028 if not utilized to offset taxable income, and $13,893,000 may be carried forward indefinitely. Future changes in ownership, as defined by Section 382 of the IRC, could limit the amount of NOL carryforwards used in any one year. Also, as of December 31, 2019, the Company had state net operating loss carryforwards of approximately $42,211,000 , which begin to expire in 2028 if not utilized to offset state taxable income. In general, under Section 382 and 383 of the IRC, a corporation that undergoes an “ownership change” is subject to limitations on its ability to utilize its pre-change NOLs and certain tax credits, to offset future taxable income and tax. In general, an ownership change occurs if the aggregate stock ownership of certain stockholders changes by more than 50 percentage points over such stockholders’ lowest percentage of ownership during the testing period (generally three years). The Company performed a Section 382 analysis from inception through the year ended December 31, 2019 and concluded the Company had experienced an ownership change in 2011 and 2014. These changes in ownership did not result in the expiration of any NOLs or R&D credits. However, future changes in ownership may further limit the ability of the Company to utilize its NOL carryforwards and R&D tax credit carryforwards. At December 31, 2019 and 2018, the Company placed a valuation allowance of $12,420,000 and $14,375,000 , respectively, against the entirety of its net deferred tax asset balance, as the Company has not determined that it is more likely than not to be realized. The Company assessed whether it had any significant uncertain tax positions related to open tax years and concluded there were none. Accordingly, no reserve for uncertain tax positions has been recorded as of December 31, 2019 and 2018. The Company is generally no longer subject to tax examinations for U.S. federal income tax purposes for fiscal years prior to 2016 and fiscal years prior to 2014 for multiple state jurisdictions. However, since the Company has been in an NOL position since 2008, the Company’s 2008 to 2015 federal tax returns and its 2008 to 2013 state tax returns are potentially subject to examination adjustments to the extent of those NOL carryforwards.

Selected Quarterly Financial Da

Selected Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Financial Data (Unaudited)	Selected Quarterly Financial Data (Unaudited) The following is a summary of selected unaudited quarterly financial data for the years ended December 31, 2019 and 2018 (in thousands, except per share data): Year Ended December 31, 2019 First Quarter Second Quarter Third Quarter Fourth Quarter Total Year Net revenues $ 8,717 $ 10,739 $ 14,774 $ 17,635 $ 51,865 Gross margin $ 7,119 $ 8,746 $ 13,066 $ 15,624 $ 44,555 Net income (loss) (1) $ (1,358 ) $ (1,269 ) $ 5,849 $ 2,055 $ 5,277 Net income (loss) attributable to common shareholders (1) $ (2,342 ) $ (2,265 ) $ 5,543 $ 2,055 $ 2,991 Earnings (loss) per share (3) : Basic $ (1.22 ) $ (1.05 ) $ 0.43 $ 0.12 $ 0.35 Diluted $ (1.22 ) $ (1.05 ) $ 0.05 $ 0.11 $ (0.21 ) Year Ended December 31, 2018 First Quarter Second Quarter Third Quarter Fourth Quarter Total Year Net revenues (2) $ 3,659 $ 3,979 $ 3,712 $ 11,436 $ 22,786 Gross margin (2) $ 2,406 $ 2,652 $ 2,361 $ 10,070 $ 17,489 Net income (loss) (2) $ (3,630 ) $ (3,155 ) $ (3,450 ) $ 3,868 $ (6,367 ) Net income (loss) attributable to common shareholders (2) $ (4,489 ) $ (4,080 ) $ (4,456 ) $ 2,862 $ (10,163 ) Earnings (loss) per share (3) : Basic $ (2.37 ) $ (2.15 ) $ (2.33 ) $ 1.49 $ (5.33 ) Diluted $ (2.37 ) $ (2.15 ) $ (2.33 ) $ 0.38 $ (5.33 ) (1) For the third quarter of 2019, includes gain on extinguishment of debt of (in thousands) $5,213 . (2) For the fourth quarter of 2018, includes revenue recognized of (in thousands) $5,191 for tests delivered during the first three quarters of 2018 for which the requirements to release the constraint on variable consideration were not met until the fourth quarter of 2018 in connection with the issuance of the LCD for DecisionDx-Melanoma and establishment of a Medicare reimbursement rate. (3) Basic and diluted earnings (loss) per share are computed independently for each quarterly and annual period presented. Therefore, t he sum of the quarterly basic and diluted earnings (loss) per share amounts may not equal annual basic and diluted earnings (loss) per share.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2019
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events On January 15, 2020 and February 14, 2020, the Company granted to various employees, options to purchase an aggregate of 17,500 and 135,000 shares, respectively, of our common stock at an exercise price of $31.97 and $31.80 per share, respectively. The option awards were granted pursuant to the 2019 Plan, have a ten -year term and vest over a four -year period (with 25% vesting after one year from the vesting start date and the remainder vesting in 36 equal monthly installments thereafter). On February 28, 2020, the Company issued 39,987 shares of its common stock under a scheduled purchase under the ESPP. The shares were purchased at a price of $15.09 and funded through employee payroll deductions. On February 28, 2020 and March 4, 2020, the Compa ny and the Lenders amended the 2018 LSA, as discussed in Note 8.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Basis of Presentation	The Company’s financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (‘‘U.S. GAAP’’). The Company has no subsidiaries and all operations are conducted by the Company.
Use of Estimates	The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Significant items subject to such estimates include revenue recognition, the determination of fair value of the Company’s preferred stock warrants and convertible debt embedded derivatives, the valuation of stock options, assessing future tax exposure and the realization of deferred tax assets, the useful lives and recoverability of property and equipment, and contingent liabilities. The Company bases these estimates on historical and anticipated results, trends, and various other assumptions that the Company believes are reasonable under the circumstances, including assumptions as to future events. These estimates form the basis for making judgments about the carrying values of assets and liabilities and recorded revenues and expenses that are not readily apparent from other sources. Actual results could differ from those estimates and assumptions.
Operating Segments	Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision maker, or decision-making group, in making decisions on how to allocate resources and assess performance. The Company views its operations and manages its business as one operating segment. All revenues are attributable to U.S.-based operations and all assets are held in the United States.
Cash and Cash Equivalents	Cash equivalents consist of short-term, highly liquid investments with original maturities of three months or less. Cash equivalents consist primarily of amounts invested in money market accounts.
Concentrations of Credit Risk	A majority of the Company’s cash and cash equivalents are deposited with a single financial institution.
Revenue Recognition, Cost of Sales	Cost of sales is expensed as incurred and includes direct labor costs, equipment, supplies, materials and infrastructure expenses associated with testing tissue samples, third-party lab processing and service costs, third-party collection costs, and shipping charges to transport samples. Revenue is recognized in accordance with Financial Accounting Standards Board (‘‘FASB’’) Accounting Standards Codification (‘‘ASC’’) Topic 606, Revenue from Contracts with Customers (‘‘ASC 606’’). In accordance with ASC 606, the Company follows a five-step process to recognize revenues: (1) identify the contract with the customer, (2) identify the performance obligations, (3) determine the transaction price, (4) allocate the transaction price to the performance obligations and (5) recognize revenues when the performance obligations are satisfied. All of the Company’s revenues from contracts with customers are associated with the provision of diagnostic and prognostic cancer testing services. Most of the Company’s revenues are attributable to DecisionDx-Melanoma for cutaneous melanoma. The Company also provides a test for uveal melanoma, DecisionDx-UM. Information on the disaggregation of revenues by the Company’s significant third-party payors is included under Payor Concentration below. The Company has determined that it has a contract with the patient when the treating clinician orders the test. The Company’s contracts generally contain a single performance obligation, which is the delivery of the test report, and the Company satisfies its performance obligation at a point in time upon the delivery of the test report to the treating physician, at which point the Company can bill for the report. The amount of revenue recognized reflects the amount of consideration to which the Company expects to be entitled (the ‘‘transaction price’’) and considers the effects of variable consideration, which is discussed further below. Once the Company satisfies its performance obligations and bills for the service, the timing of the collection of payments may vary based on the payment practices of the third-party payor and the existence of contractually established reimbursement rates. Most of the payments for the Company’s services are made by third-party payors, including Medicare and commercial health insurance carriers. Certain contracts contain a contractual commitment of a reimbursement rate that differs from the Company’s list prices. However, absent a contractually committed reimbursement rate with a commercial carrier or governmental program, the Company’s diagnostic tests may or may not be covered by these entities’ existing reimbursement policies. In addition, patients do not enter into direct agreements with the Company that commit them to pay any portion of the cost of the tests in the event that their insurance provider declines to reimburse the Company. The Company may pursue, on a case-by-case basis, reimbursement from such patients in the form of co-payments and co-insurance, in accordance with the contractual obligations that the Company has with the insurance carrier or health plan. These situations may result in a delay in the collection of payments. The Medicare claims that are covered by policy under a Local Coverage Determination (‘‘LCD’’) are generally paid at the established rate by the Company’s Medicare contractor within 30 days from receipt. Medicare claims that were either submitted to Medicare prior to the LCD coverage commencement date or are not covered by the terms of the LCD but meet the definition of being medically reasonable and necessary pursuant to the controlling Section 1862(a)(1)(A) of the Social Security Act are generally appealed and may ultimately be paid at the first (termed ‘‘redetermination’’), second (termed ‘‘reconsideration’’) or third level of appeal (de novo hearing with an Administrative Law Judge (“ALJ”)). A successful appeal at any of these levels results in payment. In the absence of LCD coverage or contractually established reimbursements rates, the Company has concluded that its contracts include variable consideration because the amounts paid by Medicare or commercial health insurance carriers may be paid at less than the Company’s standard rates or not paid at all, with such differences considered implicit price concessions. Variable consideration attributable to these price concessions is measured at the expected value using the ‘‘most likely amount’’ method under ASC 606. The amounts are determined by historical average collection rates by test type and payor category taking into consideration the range of possible outcomes, the predictive value of the Company’s past experiences, the time period of when uncertainties expect to be resolved and the amount of consideration that is susceptible to factors outside of the Company’s influence, such as the judgment and actions of third parties. Such variable consideration is included in the transaction price only to the extent it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur when the uncertainties with respect to the amount are resolved. Variable consideration may be constrained and excluded from the transaction price in situations where there is no contractually agreed upon reimbursement coverage or in the absence of a predictable pattern and history of collectability with a payor. Variable consideration for Medicare claims is deemed to be fully constrained when the payment of such claims is subject to approval by an ALJ at an appeal hearing, due to factors outside the Company’s influence (i.e., judgment or actions of third parties) and the uncertainty of the amount to be received is not expected to be resolved for a long period of time. Variable consideration is evaluated each reporting period and adjustments are recorded as increases or decreases in revenues. Included in revenues for the years ended December 31, 2019 and 2018 were $2,493,000 and $343,000 , respectively, of revenue increases associated with changes in estimated variable consideration related to performance obligations satisfied in previous periods. These amounts include (i) adjustments for actual collections versus estimated amounts and (ii) cash collections and the related recognition of revenue in current period for tests delivered in prior periods due to the release of the constraint on variable consideration. Because the Company’s contracts with customers have an expected duration of one year or less, the Company has elected the practical expedient in ASC 606 to not disclose information about its remaining performance obligations. Any incremental costs to obtain contracts are recorded as selling, general and administrative expense as incurred due to the short duration of the Company’s contracts.
Accounts Receivable	The Company classifies accounts receivable balances that are expected to be paid more than one year from the balance sheet date as non-current assets. The estimated timing of payment utilized as a basis for classification as non-current is determined by analyses of historical payor-specific payment experience, adjusted for known factors that are expected to change the timing of future payments.
Allowance for Doubtful Accounts	The Company accrues an allowance for doubtful accounts against its accounts receivable when it is probable that an account is not collectible, based on write off history, credit risk of specific accounts, aging analysis and other information available on specific accounts. The Company generally does not perform evaluations of customers’ financial condition and generally does not require collateral. Accounts receivable are written off when all efforts to collect the balance have been exhausted. Historically, the Company’s bad debt expense has not been significant. The allowance for doubtful accounts was zero as of December 31, 2019 and 2018 . Adjustments for implicit price concessions attributable to variable consideration, as discussed above, are incorporated into the measurement of the accounts receivable balances and are not part of the allowance for doubtful accounts.
Inventory	The Company carries an inventory of test supplies in the Phoenix, Arizona laboratory. The inventory is carried at the lower of weighted average cost and net realizable value and expensed through cost of sales as the supplies are used.
Property and Equipment	Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation is computed using the straight-line method over the estimated useful lives of the assets, generally between five and ten years . Leasehold improvements are amortized using the straight-line method over the shorter of the estimated useful life of the asset or the term of the lease. The Company’s leasehold improvements primarily relate to its office and laboratory in Phoenix, Arizona, and are generally being amortized through the end of the lease term in July 2027. Maintenance and repairs are charged to expense as incurred, and material improvements are capitalized. When assets are retired or otherwise disposed of, the cost and accumulated depreciation are removed from the balance sheet and any resulting gain or loss is reflected in the statements of operations and comprehensive loss in the period realized.
Patent Rights Licenses	The Company capitalizes the purchase of material licenses that grant interest in and to certain patent rights owned primarily by research and education institutions. These costs are amortized using the straight-line method over the shorter of the period of expected commercial benefit or the life of the underlying patent. Amortization of patent license costs is charged to research and development expense.
Long-Lived Assets	The Company reviews long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of the assets may not be recoverable. An impairment loss is recognized when the total of estimated future undiscounted cash flows, expected to result from the use of the asset and its eventual disposition, are less than the carrying amount. Impairment, if any, would be calculated based on the excess of the carrying amount of the long-lived asset over the long-lived asset’s fair value. There were no impairment charges recognized for the years ended December 31, 2019 and 2018.
Fair Value of Financial Instruments	The carrying amount of the Company’s long-term debt approximates fair value due to its variable market interest rate and management’s opinion that current rates and terms that would be available to the Company with the same maturity and security structure would be essentially equivalent to that of the Company’s long-term debt. This estimated fair value is a ‘‘Level 3’’ fair value measurement, as defined in Note 10.
Research and Development	Research and development costs are charged to operations as incurred. Advance payments for goods and services that will be used in future research and development activities are expensed when the activity has been performed or when the goods have been received rather than when the payment is made. Upfront and milestone payments due to third parties that perform research and development services on behalf of the Company will be expensed as services are rendered or when the milestone is achieved. Research and development costs include, but are not limited to, payroll and personnel-related expenses, stock-based compensation expense, materials, laboratory supplies, and consulting costs.
Selling, General and Administrative Expenses	Selling, general and administrative (“SG&A”) expenses are attributable to sales, marketing, executive, finance and accounting, legal and human resources functions. These expenses consist of personnel costs (including salaries, employee benefit costs, bonuses and equity-based compensation expenses), customer services expenses, direct marketing expenses, educational and promotional expenses, market research, audit and legal expenses, and consulting. The Company expenses all SG&A costs as incurred.
Accrued Compensation, Stock-Based Compensation	The Company accrues for liabilities under discretionary employee and executive bonus plans. These estimated compensation liabilities are based on progress against corporate objectives approved by the Board of Directors, compensation levels of eligible individuals, and target bonus percentage levels. The Board of Directors reviews and evaluates the performance against these objectives and ultimately determines what discretionary payments are made. The Company also accrues for liabilities under employee sales incentive bonus plans with accruals based on performance achieved to date compared to established targets. As of December 31, 2019 and 2018 , the Company accrued approximately $4,785,000 and $3,197,000 , respectively, for liabilities associated with these bonus plans. These amounts are classified as current or noncurrent accrued liabilities in the balance sheets based on the expected timing of payment. Stock-based compensation expense for equity instruments issued to employees is measured based on the grant-date fair value of the awards. The fair value of employee stock options and offerings under the 2019 Employee Stock Purchase Plan (the “ESPP”) are estimated on the date of grant using the Black-Scholes option-pricing valuation model. The Company recognizes compensation costs on a straight-line basis for all employee stock-based compensation awards over the requisite service period of the awards. For options, the requisite service period is generally the awards’ vesting period (typically four years ). For the ESPP, the requisite service period is generally the period of time from the offering date to the purchase date. Forfeitures are accounted for as they occur.
Retirement Plan	The Company has an Internal Revenue Code (“IRC”) Section 401(k) profit sharing plan (the “Plan”) for eligible employees. The Plan is funded by employee contributions and provides for discretionary contributions in the form of matching and/or profit-sharing contributions.
Income Taxes	The Company recognizes deferred tax assets and liabilities for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using statutory tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in the period that includes the statutory enactment date. Valuation allowances are established to reduce deferred tax assets when it is more likely than not that some portion or all of the deferred tax assets will not be realized. Tax benefits are recognized only for tax positions that are more likely than not to be sustained upon examination by tax authorities. The amount recognized is measured as the largest amount of benefit that is greater than 50% likely to be realized upon settlement. A liability for unrecognized tax benefits is recorded for any tax benefits claimed in the Company’s tax returns that do not meet these recognition and measurement standards. The Company’s policy for recording interest and penalties associated with uncertain tax positions is to record such items as a component of tax expense. No material amounts of tax-related interest or penalties were recorded during the years ended December 31, 2019 and 2018.
Deferred Offering Costs	Deferred offering costs consist primarily of legal and accounting fees, which are direct and incremental costs related to the IPO. Deferred offering costs of $2,517,000 , along with $5,152,000 in underwriting discounts and commissions, were offset against the gross IPO proceeds of $73,600,000 for the year ended December 31, 2019.
Comprehensive Income (Loss)	Comprehensive income (loss) is defined as a change in equity during a period from transactions and other events and circumstances from non-owner sources.
Accounting Pronouncements Yet to be Adopted	In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) (“ASU 2016-02”), which supersedes FASB ASC Topic 840, Leases (Topic 840), and provides principles for the recognition, measurement, presentation and disclosure of leases for both lessees and lessors. The new standard requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the lessee. This classification will determine whether lease expense is recognized based on an effective interest method for finance leases or on a straight-line basis over the term of the lease for operating leases. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than 12 months regardless of classification. Leases with a term of 12 months or less will be accounted for similar to existing guidance for operating leases. For companies that are not emerging growth companies (‘‘EGCs’’), ASU 2016-02 is effective for fiscal years beginning after December 15, 2018. For EGCs, the ASU was to be effective for fiscal years beginning after December 15, 2019. However, in November 2019, the FASB issued ASU 2019-10, Financial Instruments—Credit Losses (Topic 326), Derivatives and Hedging (Topic 815) and Leases (Topic 842): Effective Dates (“ASU 2019-10”), which included a one-year deferral of the effective date of ASU 2016-02 for certain entities. As a result, the ASU is now effective for EGCs for fiscal years beginning after December 15, 2020, and interim periods within fiscal years beginning after December 15, 2021. The Company expects to adopt the new standard in the fourth quarter of 2021 using the modified retrospective method, under which the Company will apply Topic 842 to existing and new leases as of January 1, 2021, but prior periods will not be restated and will continue to be reported under Topic 840 guidance in effect during those periods. The Company anticipates that the adoption will not have a material impact on its statements of operations and comprehensive income (loss) or its statements of cash flows but expects to recognize right-of-use assets and liabilities for lease obligations associated with its operating leases. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments—Credit Losses (“ASU 2016-13”), which requires the measurement of expected credit losses for financial instruments carried at amortized cost, such as accounts receivable, held at the reporting date based on historical experience, current conditions and reasonable forecasts. The main objective of this ASU is to provide financial statement users with more decision-useful information about the expected credit losses on financial instruments and other commitments to extend credit held by a reporting entity at each reporting date. In November 2018, the FASB issued ASU No. 2018-19, Codification Improvements to Topic 326, Financing Instruments—Credit Losses , which included an amendment of the effective date for nonpublic entities. For non-EGCs, ASU 2016-13 is effective for fiscal years beginning after December 15, 2019. For EGCs, the standard was to be effective for fiscal years beginning after December 15, 2021. However, in November 2019, the FASB issued ASU 2019-10, which included a one-year deferral of the effective date of ASU 2016-13 for certain entities. As a result, ASU is now effective for EGCs for fiscal years beginning after December 15, 2022, including interim periods within those fiscal years. The Company does not currently believe the adoption of this standard will have a significant impact on its financial statements, given its history of minimal bad debt expense relating to trade accounts receivable. In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (“ASU 2019-12”), which eliminates certain exceptions to the general principles in Topic 740 and simplifies other areas of the existing guidance. For non-EGCs, ASU 2019-12 is effective for fiscal years beginning after December 15, 2020, and interim periods within those fiscal years. For EGCs, the standard is effective for fiscal years beginning after December 15, 2021, and interim periods within fiscal years beginning after December 15, 2022. Early adoption is permitted. The Company is currently evaluating the impact of ASU 2019-12 on its financial statements.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Schedules of Concentration of Risk, by Risk Factor	The Company’s significant third-party payors and their related revenues as a percentage of total revenues and accounts receivable balances are as follows: Percentage of Revenues Percentage of Accounts Receivable (current) Percentage of Accounts Receivable (non-current) Year Ended December 31, As of December 31, As of December 31, 2019 2018 2019 2018 2019 2018 Medicare 49 % 36 % 7 % 54 % — % — % Medicare Advantage plans 29 % 17 % 41 % 9 % 18 % 18 % United Healthcare 6 % 12 % 9 % 7 % — % 15 % BlueCross BlueShield plans 6 % 18 % 25 % 18 % 46 % 41 %

Earnings (Loss) Per Share (Tabl

Earnings (Loss) Per Share (Tables)	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	The following table shows the computation of basic and diluted earnings (loss) per share for the years ended December 31, 2019 and 2018 (in thousands, except per share data): Years Ended December 31, 2019 2018 Numerator: Net income (loss) attributable to common stockholders $ 2,991 $ (10,163 ) Assumed conversion of convertible promissory notes (1) : Subtract: Extinguishment gain (5,213 ) — Add: Interest expense and change in fair value of embedded derivative 420 — Numerator for diluted loss per share $ (1,802 ) $ (10,163 ) Denominator: Weighted-average common shares outstanding, basic 8,584 1,906 Assumed conversion of convertible promissory notes (1) 74 — Weighted-average common shares outstanding, diluted 8,658 1,906 Earnings (loss) per share attributable to common stockholders: Basic $ 0.35 $ (5.33 ) Diluted $ (0.21 ) $ (5.33 ) (1) For the year ended December 31, 2019 , reflects the assumed conversion of the Q1 2019 Notes (as defined in Note 7) into shares of common stock beginning July 1, 2019, in accordance with the requirements in ASC 260, Earnings per Share , for contingently issuable shares due to the contingency not being met until the third quarter of 2019. The July 2019 Note (as defined in Note 7), was excluded from the computation of diluted earnings (loss) per share prior to its conversion on July 29, 2019 in connection with the IPO, as disclosed below.
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	The table below provides the weighted-average number of potential common shares associated with outstanding securities not included in the Company’s calculation of diluted earnings (loss) per share for the years ended December 31, 2019 and 2018 because to do so would be antidilutive (in thousands): Years Ended December 31, 2019 2018 Convertible preferred stock 4,679 7,845 Convertible promissory note (1) 33 — Stock options 1,820 1,429 Common stock warrants 41 — Preferred stock warrants 80 132 Employee stock purchase plan 24 — Total 6,677 9,406 (1) Associated with the July 2019 Note.

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property and equipment, net consisted of the following (in thousands): As of December 31, 2019 2018 Lab equipment $ 1,563 $ 1,153 Computer equipment 887 629 Leasehold improvements 635 554 Furniture and fixtures 178 102 Total 3,263 2,438 Less accumulated depreciation (1,203 ) (909 ) Property and equipment, net $ 2,060 $ 1,529 Depreciation expense was recorded in the statements of operations and comprehensive income (loss) as follows (in thousands): Years Ended December 31, 2019 2018 Cost of sales $ 277 $ 233 Research and development 7 4 Selling, general and administrative 70 50 Total $ 354 $ 287

Intangible Assets, Net (Tables)

Intangible Assets, Net (Tables)	12 Months Ended
	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Finite-Lived Intangible Assets	Intangible assets consist of capitalized license costs as follows (in thousands): As of December 31, 2019 2018 Value Weighted-Average Remaining Life (Years) Value Weighted-Average Remaining Life (Years) Licenses $ 275 0 $ 275 0 Accumulated amortization (275 ) (271 ) Intangible assets, net $ — $ 4

Other Accrued Liabilities (Tabl

Other Accrued Liabilities (Tables)	12 Months Ended
	Dec. 31, 2019
Payables and Accruals [Abstract]
Schedule of Accrued Liabilities	Other accrued liabilities consisted of the following (in thousands) : As of December 31, 2019 2018 Accrued state income taxes $ 79 $ 9 Accrued interest 184 185 Accrued royalties 169 240 Accrued service fees 1,162 281 Employee stock purchase plan contributions 218 — Total $ 1,812 $ 715

Convertible Promissory Notes (T

Convertible Promissory Notes (Tables)	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Schedule of Short-term Debt	The following table summarizes the aggregate values recorded for the Q1 2019 Notes as of their original issuance dates. As noted above, the Q1 2019 Notes were converted into shares of common stock in connection with the closing of the IPO on July 29, 2019 (in thousands) . At Original Issuance (1) Liability component: Principal (including $4,756 with related parties) $ 11,770 Unamortized issuance costs (75 ) Unamortized discount from beneficial conversion feature (8,378 ) Unamortized discount from embedded derivative (2,816 ) Net carrying amount of the liability component $ 501 Embedded derivative liability $ 2,816 Equity Component: Carrying value of beneficial conversion feature recorded in additional paid-in capital $ 8,378 (1) The Q1 2019 Notes were issued on January 31, 2019, February 12, 2019 and February 27, 2019.
Derivatives Not Designated as Hedging Instruments	The amounts recognized in net income for the year ended December 31, 2019 for the embedded derivative liability are as follows (in thousands) : Gain (Loss) Recognized in Net Income Statement of Operations and Comprehensive Income (Loss) Location Year Ended December 31, 2019 Derivatives Not Classified as Hedging Instruments Embedded derivative in convertible promissory notes Other expense, net $ (237 )

Long-Term Debt (Tables)

Long-Term Debt (Tables)	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Schedule of Long-term Debt Instruments	The Company’s long-term debt consists of term debt and a revolving line of credit and are presented in the table below (in thousands): As of December 31, 2019 2018 Term debt $ 26,688 $ 21,350 Revolving line of credit — 5,000 Total principal amount 26,688 26,350 Unamortized discount and issuance costs (1,566 ) (1,850 ) Total long-term debt 25,122 24,500 Less: Current portion of long-term debt (5,833 ) — Total long-term debt, less current portion $ 19,289 $ 24,500
Schedule of Maturities of Long-term Debt	Future maturities of principal amounts on long-term debt as of December 31, 2019 are as follows (in thousands): Years Ending December 31, 2020 $ 5,833 2021 10,000 2022 10,855 2023 — 2024 — Total $ 26,688

Operating Leases (Tables)

Operating Leases (Tables)	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Schedule of Future Minimum Payments for Operating Leases	Future non-cancellable commitments under all operating leases are as follows (in thousands): Years Ending December 31, 2020 $ 754 2021 995 2022 993 2023 1,029 2024 999 Thereafter 1,625 $ 6,395

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Fair Value, Liabilities, Measured on Recurring Basis	The table below provides information (in thousands), by level within the fair value hierarchy, of the Company’s financial assets and liabilities that are accounted for at fair value on a recurring basis as of December 31, 2018 . There were no financial assets and liabilities accounted for at fair value on a recurring basis as of December 31, 2019 . As of December 31, 2018 Quoted Prices in Active Markets for Identical Items (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Liabilities: Preferred stock warrants $ — $ — $ 1,194 $ 1,194
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation	The following table discloses the summary of changes in the fair value of the Level 3 fair value measurements (in thousands): Preferred stock warrant liability Embedded derivative liability in the Q1 2019 Notes The July 2019 Note Balance, January 1, 2018 $ 525 $ — $ — Issuance of warrants 632 — — Change in fair value included in net loss 272 — — Exercised warrants (235 ) — — Balance, December 31, 2018 $ 1,194 $ — $ — Issuance of convertible promissory notes — 2,816 9,236 Change in fair value included in net income 619 237 2,077 Extinguishment of convertible promissory notes and exercise of warrants (68 ) (3,053 ) (11,313 ) Reclassification of preferred stock warrant liability to stockholders’ equity (1,745 ) — — Balance, December 31, 2019 $ — $ — $ —
Fair Value Measurement Inputs and Valuation Techniques	The fair value of the warrants to purchase shares of Series A, Series B, Series E-1, Series E-2, Series E-2A, Series E-3, and Series F redeemable convertible preferred stock was estimated by management using the Black-Scholes option pricing model with the following assumptions: December 31, 2018 Average expected life (years) 9 Expected stock price volatility 64% Risk-free interest rate 2.51% - 2.69% Dividend yield —%

Convertible Preferred Stock a_2

Convertible Preferred Stock and Preferred Stock Warrants (Tables)	12 Months Ended
	Dec. 31, 2019
Stockholders' Equity And Temporary Equity [Abstract]
Temporary Equity	Convertible preferred stock consisted of the following (in thousands, except share and per share data): Convertible preferred stock As of December 31, 2018 Shares Authorized Shares Issued and Outstanding Original Issue Price per Share Original Issue Value Accumulated and Undeclared Dividends Aggregate Liquidation Preference Carrying Value Series C 503,056 503,056 $3.4800 $ 1,751 $ 667 $ 2,417 $ 1,501 Redeemable convertible preferred stock As of December 31, 2018 Shares Authorized Shares Issued and Outstanding Original Issue Price per Share Original Issue Value Accumulated and Undeclared Dividends Aggregate Liquidation Preference Carrying Value Series A 533,711 533,711 $2.1400 $ 1,142 $ 713 $ 1,856 $ 1,142 Series B 816,654 816,654 $2.2500 1,837 983 2,820 1,932 Series D 756,416 756,416 $3.7700 2,852 1,340 4,191 2,852 Series E-1 842,641 829,642 $3.7700 3,128 1,095 4,223 3,099 Series E-2 949,725 934,433 $4.5776 4,277 1,503 5,780 4,277 Series E-2A 27,306 27,306 $4.5776 125 39 164 125 Series E-3 830,554 824,000 $5.3405 4,401 1,364 5,764 4,394 Series F 4,883,486 4,734,613 $5.8208 27,559 5,212 32,772 27,174 Total 9,640,493 9,456,775 $ 45,321 $ 12,249 $ 57,570 $ 44,995 The holders of the outstanding shares of Series A, Series B, Series C, Series D, Series E-1, Series E-2, Series E-2A, Series E-3, and Series F convertible preferred stock were entitled to receive, when and if declared by the Board of Directors, a cash dividend in the following order of preference and at the rates per annum noted: Convertible Preferred Stock Class Annual Dividend Rate Series F $ 0.46570 Series E-3 $ 0.42720 Series E-2A $ 0.36620 Series E-2 $ 0.36620 Series E-1 $ 0.30160 Series D $ 0.30160 Series C $ 0.27840 Series B $ 0.18000 Series A $ 0.17120
Schedule of Warrants Outstanding	Warrants to purchase redeemable convertible preferred shares consisted of the following: As of December 31, 2018 Warrants Year of First Issuance Shares Exercise Price Year of Expiration Exercised Expired Outstanding Series A Preferred Stock 2008 108,057 $2.1400 2015 (96,375 ) (11,682 ) — Series B Preferred Stock 2010 86,667 $2.2500 2017 (86,667 ) — — Series E-1 Preferred Stock 2014 16,249 $3.7700 2024 (3,250 ) — 12,999 Series E-2 Preferred Stock 2014 15,292 $4.5776 2024 — — 15,292 Series E-3 Preferred Stock 2015 6,554 $5.3405 2024 — — 6,554 Series F Preferred Stock 2016 103,090 $5.8208 2026-2028 — — 103,090 Series F Preferred Stock 2018 67,233 $0.0100 2023 (32,951 ) — 34,282 Total 403,142 (219,243 ) (11,682 ) 172,217 Information about common stock warrants outstanding as of December 31, 2019 is presented in the table below: As of December 31, 2019 Expiration date Number of shares Exercise price July 12, 2026 209,243 $ 0.001 March 31, 2027 26,428 $ 7.10 November 30, 2028 8,809 $ 7.10 Total 244,480 The common stock warrants are classified as stockholders’ equity and no adjustments are recorded for changes in fair value. There were no common stock warrants outstanding as of December 31, 2018 .

Stockholders' Equity (Deficit)

Stockholders' Equity (Deficit) (Tables)	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Schedule of Common Stock Warrants Outstanding	Warrants to purchase redeemable convertible preferred shares consisted of the following: As of December 31, 2018 Warrants Year of First Issuance Shares Exercise Price Year of Expiration Exercised Expired Outstanding Series A Preferred Stock 2008 108,057 $2.1400 2015 (96,375 ) (11,682 ) — Series B Preferred Stock 2010 86,667 $2.2500 2017 (86,667 ) — — Series E-1 Preferred Stock 2014 16,249 $3.7700 2024 (3,250 ) — 12,999 Series E-2 Preferred Stock 2014 15,292 $4.5776 2024 — — 15,292 Series E-3 Preferred Stock 2015 6,554 $5.3405 2024 — — 6,554 Series F Preferred Stock 2016 103,090 $5.8208 2026-2028 — — 103,090 Series F Preferred Stock 2018 67,233 $0.0100 2023 (32,951 ) — 34,282 Total 403,142 (219,243 ) (11,682 ) 172,217 Information about common stock warrants outstanding as of December 31, 2019 is presented in the table below: As of December 31, 2019 Expiration date Number of shares Exercise price July 12, 2026 209,243 $ 0.001 March 31, 2027 26,428 $ 7.10 November 30, 2028 8,809 $ 7.10 Total 244,480 The common stock warrants are classified as stockholders’ equity and no adjustments are recorded for changes in fair value. There were no common stock warrants outstanding as of December 31, 2018 .

Stock Incentive Plans and Sto_2

Stock Incentive Plans and Stock Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
Share-based Payment Arrangement, Option, Activity	Activity under the Company’s stock plans for the years ended December 31, 2019 and 2018 is set forth below: Weighted-Average Shares Available for Grant Stock Options Outstanding Exercise Price Remaining Contractual Term (Years) Aggregate Intrinsic Value (in thousands) Balance as of December 31, 2017 551,918 1,175,987 $ 1.79 Additional options authorized 410,172 — — Granted (580,402 ) 580,402 2.39 Exercised — (19,755 ) 1.91 Forfeited/Cancelled 77,038 (77,038 ) 1.82 Balance as of December 31, 2018 458,726 1,659,596 $ 1.99 Additional options authorized 2,075,898 — — Granted (1,711,325 ) 1,711,325 19.41 Exercised — (693,127 ) 1.70 Forfeited/Cancelled 39,828 (39,828 ) 6.36 Balance as of December 31, 2019 863,127 2,637,966 $ 13.30 8.64 $ 55,578 Exercisable at December 31, 2019 (1 ) 590,104 $ 2.20 6.11 $ 18,984 (1) Vested and exercisable options. Additionally, outstanding unvested options to purchase an aggregate of 126,044 shares of common stock with a weighted-average exercise price of $2.39 per share may be exercised prior to vesting as of December 31, 2019 under early-exercise provisions. In the event of such exercise, the shares obtained upon exercise would be restricted and subject to forfeiture prior to vesting. No such early exercises have occurred as of December 31, 2019 .
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions	The following table sets forth the assumptions used to determine the fair value of stock options: Years Ended December 31, 2019 2018 Average expected term (years) 6 6 Expected stock price volatility 56.74% - 60.17% 57.77% - 58.29% Risk-free interest rate 1.63% - 2.47% 2.77% - 3.13% Dividend yield —% —% The following table sets forth assumptions used to determine the fair value of the purchase rights issued under the ESPP: Years Ended December 31, 2019 2018 Average expected term (years) 1.2 Not applicable Expected stock price volatility 61.12% - 68.89% Not applicable Risk-free interest rate 1.56% - 1.80% Not applicable Dividend yield —% Not applicable
Share-based Payment Arrangement, Expensed and Capitalized, Amount	Stock-based compensation expense related to stock options and the ESPP is included in the statements of operations and comprehensive income (loss) as follows (in thousands): Years Ended December 31, 2019 2018 Cost of sales $ 170 $ 24 Research and development 165 56 Selling, general and administrative 914 214 Total stock-based compensation expense $ 1,249 $ 294

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Schedule of Components of Income Tax Expense	The components of income tax expense are as follows (in thousands): Years Ended December 31, 2019 2018 Current tax expense U.S. Federal $ — $ — State and local 72 9 Total current 72 9 Deferred tax expense U.S. Federal — — State and local — — Total deferred — — Total income tax expense $ 72 $ 9
Schedule of Effective Income Tax Rate Reconciliation	The differences between income taxes expected at the U.S. federal statutory rate (21%) and the reported income tax expense are summarized as follows (in thousands): Years Ended December 31, 2019 2018 Pre-tax income (loss) $ 5,349 $ (6,358 ) U.S. federal taxes at statutory rate 1,123 (1,335 ) State income taxes 958 (1,174 ) Mark-to-market losses 566 57 Non-deductible meals 224 119 Convertible debt interest 95 — Research and development (“R&D”) tax credit (251 ) — Change in valuation allowance (2,747 ) 2,278 Stock-based compensation 65 53 Other 39 11 Total income tax expense $ 72 $ 9
Schedule of Deferred Tax Assets and Liabilities	Significant components of deferred tax assets and liabilities are as follows (in thousands): As of December 31, 2019 2018 Deferred tax assets: Net operating loss (“NOL”) carryforwards $ 14,077 $ 16,184 Accounts payable 456 390 Accrued liabilities 1,817 1,432 R&D tax credit 993 715 Intangible assets 50 61 Stock-based compensation 127 12 Charitable contributions 2 4 Total deferred tax assets 17,522 18,798 Less valuation allowance (12,420 ) (14,375 ) Deferred tax assets, net $ 5,102 $ 4,423 Deferred tax liabilities: Accounts receivable $ (3,796 ) $ (3,249 ) Prepaid expenses (757 ) (378 ) Property and equipment (246 ) (131 ) Section 481(a) adjustment (cash to accrual) (303 ) (665 ) Total deferred tax liabilities (5,102 ) (4,423 ) Net deferred tax asset (liability) $ — $ —

Selected Quarterly Financial _2

Selected Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information	The following is a summary of selected unaudited quarterly financial data for the years ended December 31, 2019 and 2018 (in thousands, except per share data): Year Ended December 31, 2019 First Quarter Second Quarter Third Quarter Fourth Quarter Total Year Net revenues $ 8,717 $ 10,739 $ 14,774 $ 17,635 $ 51,865 Gross margin $ 7,119 $ 8,746 $ 13,066 $ 15,624 $ 44,555 Net income (loss) (1) $ (1,358 ) $ (1,269 ) $ 5,849 $ 2,055 $ 5,277 Net income (loss) attributable to common shareholders (1) $ (2,342 ) $ (2,265 ) $ 5,543 $ 2,055 $ 2,991 Earnings (loss) per share (3) : Basic $ (1.22 ) $ (1.05 ) $ 0.43 $ 0.12 $ 0.35 Diluted $ (1.22 ) $ (1.05 ) $ 0.05 $ 0.11 $ (0.21 ) Year Ended December 31, 2018 First Quarter Second Quarter Third Quarter Fourth Quarter Total Year Net revenues (2) $ 3,659 $ 3,979 $ 3,712 $ 11,436 $ 22,786 Gross margin (2) $ 2,406 $ 2,652 $ 2,361 $ 10,070 $ 17,489 Net income (loss) (2) $ (3,630 ) $ (3,155 ) $ (3,450 ) $ 3,868 $ (6,367 ) Net income (loss) attributable to common shareholders (2) $ (4,489 ) $ (4,080 ) $ (4,456 ) $ 2,862 $ (10,163 ) Earnings (loss) per share (3) : Basic $ (2.37 ) $ (2.15 ) $ (2.33 ) $ 1.49 $ (5.33 ) Diluted $ (2.37 ) $ (2.15 ) $ (2.33 ) $ 0.38 $ (5.33 ) (1) For the third quarter of 2019, includes gain on extinguishment of debt of (in thousands) $5,213 . (2) For the fourth quarter of 2018, includes revenue recognized of (in thousands) $5,191 for tests delivered during the first three quarters of 2018 for which the requirements to release the constraint on variable consideration were not met until the fourth quarter of 2018 in connection with the issuance of the LCD for DecisionDx-Melanoma and establishment of a Medicare reimbursement rate. (3) Basic and diluted earnings (loss) per share are computed independently for each quarterly and annual period presented. Therefore, t he sum of the quarterly basic and diluted earnings (loss) per share amounts may not equal annual basic and diluted earnings (loss) per share.

Organization and Description _2

Organization and Description of Business (Details) $ / shares in Units, $ in Thousands	Jul. 29, 2019USD ($)$ / sharesshares	Jul. 11, 2019	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Debt Instrument [Line Items]
Reverse stock split, conversion ratio		0.8203
Proceeds from initial public offering of common stock, net of underwriting discounts, commissions and issuance costs	$ 65,900		$ 65,931	$ 0
Accumulated deficit			52,212	57,489
Cash and cash equivalents			$ 98,845	$ 4,479
IPO
Debt Instrument [Line Items]
Common stock issued and sold (in shares) | shares	4,600,000
Common stock offering price (in dollars per share) | $ / shares	$ 16
Over-Allotment Option
Debt Instrument [Line Items]
Common stock issued and sold (in shares) | shares	600,000

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Narrative (Details)	Jul. 29, 2019USD ($)	Sep. 30, 2019USD ($)	Sep. 30, 2018USD ($)	Dec. 31, 2019USD ($)claimsegment	Dec. 31, 2018USD ($)
Class of Stock [Line Items]
Number of operating segments | segment				1
Number of days contract with customer is generally paid				30 days
Variable consideration adjustments included in revenue		$ 2,493,000	$ 343,000
Number of claims in adjudication process | claim				2,698
Allowance for doubtful accounts				$ 0	$ 0
Long-lived assets, impairment charges				0	0
Accrued bonuses				4,785,000	3,197,000
Discretionary matching contributions				434,000	338,000
Deferred offering costs					$ 91,000
Gross proceeds from initial public offering				$ 73,600,000
IPO
Class of Stock [Line Items]
Deferred offering costs	$ 2,517,000
Sale of stock, underwriting discounts and commissions	$ 5,152,000
Minimum
Class of Stock [Line Items]
Property, plant and equipment, useful life				5 years
Maximum
Class of Stock [Line Items]
Property, plant and equipment, useful life				10 years
Stock options
Class of Stock [Line Items]
Service period				4 years

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Payor Concentration (Details) - Third-Party Payor Concentration Risk	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Medicare | Percentage of Revenues
Concentration Risk [Line Items]
Concentration risk percentage	49.00%	36.00%
Medicare | Percentage of Accounts Receivable (current)
Concentration Risk [Line Items]
Concentration risk percentage	7.00%	54.00%
Medicare | Percentage of Accounts Receivable (non-current)
Concentration Risk [Line Items]
Concentration risk percentage	0.00%	0.00%
Medicare Advantage plans | Percentage of Revenues
Concentration Risk [Line Items]
Concentration risk percentage	29.00%	17.00%
Medicare Advantage plans | Percentage of Accounts Receivable (current)
Concentration Risk [Line Items]
Concentration risk percentage	41.00%	9.00%
Medicare Advantage plans | Percentage of Accounts Receivable (non-current)
Concentration Risk [Line Items]
Concentration risk percentage	18.00%	18.00%
United Healthcare | Percentage of Revenues
Concentration Risk [Line Items]
Concentration risk percentage	6.00%	12.00%
United Healthcare | Percentage of Accounts Receivable (current)
Concentration Risk [Line Items]
Concentration risk percentage	9.00%	7.00%
United Healthcare | Percentage of Accounts Receivable (non-current)
Concentration Risk [Line Items]
Concentration risk percentage	0.00%	15.00%
BlueCross BlueShield plans | Percentage of Revenues
Concentration Risk [Line Items]
Concentration risk percentage	6.00%	18.00%
BlueCross BlueShield plans | Percentage of Accounts Receivable (current)
Concentration Risk [Line Items]
Concentration risk percentage	25.00%	18.00%
BlueCross BlueShield plans | Percentage of Accounts Receivable (non-current)
Concentration Risk [Line Items]
Concentration risk percentage	46.00%	41.00%

Earnings (Loss) Per Share - Nar

Earnings (Loss) Per Share - Narrative (Details) - shares	Jul. 29, 2019	Jun. 08, 2018	May 31, 2018	Jan. 12, 2018	Dec. 31, 2019	Dec. 31, 2017
Series F
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Common stock issued and sold (in shares)		85,711	783,248	940,605		16,127
Number of shares issued upon net warrants exercised (in shares)	27,207
IPO
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Common stock issued and sold (in shares)	4,600,000
Common Stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Conversion of convertible preferred stock (in shares)	8,181,992				8,181,992
Conversion of convertible promissory notes (in shares)	1,661,106				1,661,106

Earnings (Loss) Per Share - Sch

Earnings (Loss) Per Share - Schedule of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Numerator:
Net income (loss) attributable to common stockholders	$ 2,055	$ 5,543	$ (2,265)	$ (2,342)	$ 2,862	$ (4,456)	$ (4,080)	$ (4,489)	$ 2,991	$ (10,163)
Assumed conversion of convertible promissory notes:
Subtract: Extinguishment gain		$ (5,213)							(5,213)	0
Add: Interest expense and change in fair value of embedded derivative									420	0
Numerator for diluted loss per share									$ (1,802)	$ (10,163)
Denominator:
Weighted-average common shares outstanding, basic (in shares)									8,584	1,906
Assumed conversion of convertible promissory notes (in shares)									74	0
Weighted-average common shares outstanding, diluted (in shares)									8,658	1,906
Earnings Per Share, Basic and Diluted [Abstract]
Basic (in dollars per share)	$ 0.12	$ 0.43	$ (1.05)	$ (1.22)	$ 1.49	$ (2.33)	$ (2.15)	$ (2.37)	$ 0.35	$ (5.33)
Diluted (in dollars per share)	$ 0.11	$ 0.05	$ (1.05)	$ (1.22)	$ 0.38	$ (2.33)	$ (2.15)	$ (2.37)	$ (0.21)	$ (5.33)

Earnings (Loss) Per Share - S_2

Earnings (Loss) Per Share - Schedule of Antidilutive Securities (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	6,677	9,406
Convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	4,679	7,845
Convertible promissory note
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	33	0
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	1,820	1,429
Employee stock purchase plan
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	24	0
Common Stock | Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	41	0
Preferred Stock | Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	80	132

Property and Equipment, Net - S

Property and Equipment, Net - Summary of Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Total	$ 3,263	$ 2,438
Less accumulated depreciation	(1,203)	(909)
Property and equipment, net	2,060	1,529
Lab equipment
Property, Plant and Equipment [Line Items]
Total	1,563	1,153
Computer equipment
Property, Plant and Equipment [Line Items]
Total	887	629
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total	635	554
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total	$ 178	$ 102

Property and Equipment, Net -_2

Property and Equipment, Net - Summary of Depreciation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Depreciation	$ 354	$ 287
Cost of sales
Property, Plant and Equipment [Line Items]
Depreciation	277	233
Research and development
Property, Plant and Equipment [Line Items]
Depreciation	7	4
Selling, general and administrative
Property, Plant and Equipment [Line Items]
Depreciation	$ 70	$ 50

Intangible Assets, Net - Summar

Intangible Assets, Net - Summary of Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Accumulated amortization	$ (275)	$ (271)
Intangible assets, net	0	4
Licenses
Finite-Lived Intangible Assets [Line Items]
Licenses	$ 275	$ 275
Weighted-Average Remaining Life (Years)	0 years	0 years

Intangible Assets, Net - Narrat

Intangible Assets, Net - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization of intangibles	$ 4	$ 36

Other Accrued Liabilities (Deta

Other Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Payables and Accruals [Abstract]
Accrued state income taxes	$ 79	$ 9
Accrued interest	184	185
Accrued royalties	169	240
Accrued service fees	1,162	281
Employee stock purchase plan contributions	218	0
Total	$ 1,812	$ 715

Convertible Promissory Notes -

Convertible Promissory Notes - Narrative (Details) - USD ($)	Jul. 29, 2019	Jul. 12, 2019	Jul. 03, 2019	Feb. 27, 2019	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Short-term Debt [Line Items]
Gain (loss) on extinguishment of debt					$ 5,213,000	$ 5,213,000	$ 0
Amortization of debt discounts and issuance costs						1,925,000	$ 566,000
Number of shares to be purchased by warrant (in shares)							403,142
IPO
Short-term Debt [Line Items]
Common stock offering price (in dollars per share)	$ 16
Convertible Debt | Q1 2019 Convertible Promissory Notes
Short-term Debt [Line Items]
Debt instrument, face amount				$ 11,770,000
Debt instrument, interest rate, stated percentage				8.00%
Gain (loss) on extinguishment of debt	$ 5,213,000		$ 0
Proceeds from issuance of common stock				$ 10,000,000
Debt instrument, convertible debt, percentage of purchase price upon conversion	80.00%			80.00%
Repurchase price multiplier of principal amount				2
Convertible debt, number of shares issued (in shares)	954,074
Debt instrument, convertible, conversion price (in dollars per share)	$ 12.80
Extinguishment of debt	$ 15,265,000
Amortization of debt discounts and issuance costs						$ 1,216,000
Convertible Debt | July 2019 Convertible Promissory Note
Short-term Debt [Line Items]
Debt instrument, face amount		$ 10,000,000
Debt instrument, interest rate, stated percentage		8.00%
Convertible debt, number of shares issued (in shares)	707,032
Proceeds from issuance of debt		$ 10,000,000
Debt issuance costs		764,000
Proceeds from issuance of debt, net of issuance costs		$ 9,236,000
Debt instrument, fair value	$ 11,313,000
Convertible Promissory Notes
Short-term Debt [Line Items]
Convertible promissory notes, related parties				$ 4,756,000
Series F
Short-term Debt [Line Items]
Convertible preferred stock, par value (in dollars per share)				$ 5.8208			$ 5.8208
Common Stock
Short-term Debt [Line Items]
Number of shares to be purchased by warrant (in shares)		209,243
Exercise price of warrants (in dollars per share)		$ 0.001

Convertible Promissory Notes _2

Convertible Promissory Notes - Summary of Aggregate Value of Notes (Details)	Feb. 27, 2019USD ($)
Convertible Debt | Q1 2019 Convertible Promissory Notes
Short-term Debt [Line Items]
Principal (including $4,756 with related parties)	$ 11,770,000
Unamortized issuance costs	(75,000)
Net carrying amount of the liability component	501,000
Embedded derivative liability	2,816,000
Carrying value of beneficial conversion feature recorded in additional paid-in capital	8,378,000
Convertible Promissory Notes
Short-term Debt [Line Items]
Convertible promissory notes, related parties	4,756,000
Beneficial Conversion Feature | Convertible Debt | Q1 2019 Convertible Promissory Notes
Short-term Debt [Line Items]
Unamortized discount	(8,378,000)
Embedded Derivative Financial Instruments | Convertible Debt | Q1 2019 Convertible Promissory Notes
Short-term Debt [Line Items]
Unamortized discount	$ (2,816,000)

Convertible Promissory Notes _3

Convertible Promissory Notes - Gains (Losses) of Derivative Instruments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Embedded Derivative [Line Items]
Gain (Loss) Recognized in Net Income	$ (237)	$ 0
Derivatives Not Classified as Hedging Instruments | Other expense, net
Embedded Derivative [Line Items]
Gain (Loss) Recognized in Net Income	$ (237)

Long-Term Debt - Schedule of Lo

Long-Term Debt - Schedule of Long-term Debt Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Total long-term debt	$ 26,688
Less: Current portion of long-term debt	(5,833)	$ 0
Total long-term debt, less current portion	19,289	24,500
2018 Loan And Security Agreement
Debt Instrument [Line Items]
Total principal amount	26,688	26,350
Unamortized discount and issuance costs	(1,566)	(1,850)
Total long-term debt	25,122	24,500
Less: Current portion of long-term debt	(5,833)	0
Total long-term debt, less current portion	19,289	24,500
2018 Loan And Security Agreement | Notes Payable to Banks
Debt Instrument [Line Items]
Total principal amount	26,688	21,350
2018 Loan And Security Agreement | Revolving line of credit | Line of Credit
Debt Instrument [Line Items]
Total principal amount	$ 0	$ 5,000

Long-Term Debt - Narrative (Det

Long-Term Debt - Narrative (Details)	Jun. 13, 2019USD ($)	Nov. 30, 2018USD ($)installment	Sep. 30, 2019USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Debt Instrument [Line Items]
Gain (loss) on extinguishment of debt			$ 5,213,000	$ 5,213,000	$ 0
Preferred stock warrants				$ 0	$ 1,194,000
Notes Payable to Banks | 2018 Loan And Security Agreement
Debt Instrument [Line Items]
Debt instrument, face amount		$ 20,000,000
Early termination fee		$ 497,000
Revenue target covenant, period		6 months
Gain (loss) on extinguishment of debt		$ 0
Debt instrument, applicable interest rate				8.55%	8.98%
Number of months interest-only payments are permitted		18 months
Number of equal monthly installments | installment		30
Final payment, percentage of principal				6.75%
Final payment				$ 1,687,500
Notes Payable to Banks | 2018 Loan And Security Agreement | After November 30, 2019 and on or prior to November 30, 2020
Debt Instrument [Line Items]
Prepayment fee percentage		1.50%
Notes Payable to Banks | 2018 Loan And Security Agreement | After November 30, 2020
Debt Instrument [Line Items]
Prepayment fee percentage		0.75%
Notes Payable to Banks | 2018 Loan And Security Agreement | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate		6.48%
Notes Payable to Banks | 2018 Loan and Security Agreement Amendment, Amendment issued in June 2019
Debt Instrument [Line Items]
Debt instrument, face amount	$ 5,000,000
Revenue target covenant, period	3 months
Gain (loss) on extinguishment of debt	$ 0
Revolving line of credit | Line of Credit | 2018 Loan And Security Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 5,000,000
Debt instrument, applicable interest rate					7.98%
Revolving line of credit | Line of Credit | 2018 Loan And Security Agreement | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate		5.48%
Series F Preferred Stock issued in 2018
Debt Instrument [Line Items]
Preferred stock warrants		$ 158,000
Minimum | Notes Payable to Banks | 2018 Loan And Security Agreement
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage		8.55%
Minimum | Revolving line of credit | Line of Credit | 2018 Loan And Security Agreement
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage		6.25%

Long-Term Debt - Maturities of

Long-Term Debt - Maturities of Long-Term Debt (Details) $ in Thousands	Dec. 31, 2019USD ($)
Debt Disclosure [Abstract]
2020	$ 5,833
2021	10,000
2022	10,855
2023	0
2024	0
Total long-term debt	$ 26,688

Operating Leases - Narrative (D

Operating Leases - Narrative (Details) $ in Thousands	Dec. 16, 2019	Dec. 31, 2019USD ($)renewal_option	Dec. 31, 2018USD ($)
Operating Leased Assets [Line Items]
Operating leases, rent expense | $		$ 395	$ 315
Office Headquarters
Operating Leased Assets [Line Items]
Lease arrangement, renewal term		1 year
Office Space
Operating Leased Assets [Line Items]
Lease arrangement, renewal term		5 years
Lease arrangement, term of contract		60 months
Lease arrangement, number of renewal options		1
Office And Laboratory Facility
Operating Leased Assets [Line Items]
Lease arrangement, renewal term		5 years
Lease arrangement, number of renewal options		2
Lease arrangement, extension term	48 months
Additional Office Space
Operating Leased Assets [Line Items]
Lease arrangement, renewal term		5 years
Lease arrangement, term of contract		91 months
Lease arrangement, number of renewal options		2

Operating Leases - Future Minim

Operating Leases - Future Minimum Lease Payments (Details) $ in Thousands	Dec. 31, 2019USD ($)
Leases [Abstract]
2020	$ 754
2021	995
2022	993
2023	1,029
2024	999
Thereafter	1,625
Total	$ 6,395

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Financial Assets and Liabilities at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred stock warrants	$ 0	$ 1,194
Fair Value, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred stock warrants		1,194
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Items (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred stock warrants		0
Fair Value, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred stock warrants		0
Fair Value, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred stock warrants		$ 1,194

Fair Value Measurements - Chang

Fair Value Measurements - Changes in the Level 3 Fair Value Assets and Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Preferred stock warrant liability
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 1,194	$ 525
Issuance of warrants and convertible promissory notes	0	632
Change in fair value included in net income (loss)	619	272
Extinguishment of convertible promissory notes and exercise of warrants	(68)
Exercised warrants, Reclassification of preferred stock warrant liability to stockholders’ equity	(1,745)	(235)
Ending balance	0	1,194
Embedded derivative liability in the Q1 2019 Notes
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	0	0
Issuance of warrants and convertible promissory notes	2,816	0
Change in fair value included in net income (loss)	237	0
Extinguishment of convertible promissory notes and exercise of warrants	(3,053)
Exercised warrants, Reclassification of preferred stock warrant liability to stockholders’ equity	0	0
Ending balance	0	0
The July 2019 Note
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	0	0
Issuance of warrants and convertible promissory notes	9,236	0
Change in fair value included in net income (loss)	2,077	0
Extinguishment of convertible promissory notes and exercise of warrants	(11,313)
Exercised warrants, Reclassification of preferred stock warrant liability to stockholders’ equity	0	0
Ending balance	$ 0	$ 0

Fair Value Measurements - Level

Fair Value Measurements - Level 3 Inputs (Details)	Dec. 31, 2018year
Average expected life (years)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrants outstanding, measurement input	9
Expected stock price volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrants outstanding, measurement input	0.64
Dividend yield
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrants outstanding, measurement input	0
Minimum | Risk-free interest rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrants outstanding, measurement input	0.0251
Maximum | Risk-free interest rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrants outstanding, measurement input	0.0269

Fair Value Measurements - Narra

Fair Value Measurements - Narrative (Details) - $ / shares	Dec. 31, 2019	Jul. 29, 2019
IPO
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Common stock offering price (in dollars per share)		$ 16
Next Equity Financing
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Sale of stock, probability transaction will occur	90.00%
Minimum | Valuation, Income Approach | Measurement Input, Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded derivative liability, measurement input	0.0893
Maximum | Valuation, Income Approach | Measurement Input, Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Embedded derivative liability, measurement input	0.1140

Convertible Preferred Stock a_3

Convertible Preferred Stock and Preferred Stock Warrants - Schedule of Convertible Preferred Stock (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2019	Jul. 29, 2019	Feb. 27, 2019	Dec. 31, 2017
Temporary Equity [Line Items]
Convertible preferred stock outstanding (in shares)			9,973,884
Series C
Temporary Equity [Line Items]
Shares Authorized (in shares)	503,056	0
Shares Issued (in shares)	503,056	0
Convertible preferred stock outstanding (in shares)	503,056	0			503,056
Original Issue Price per Share (in dollars per share)	$ 3.48
Original Issue Value	$ 1,751
Accumulated and Undeclared Dividends	667
Aggregate Liquidation Preference	2,417	$ 0
Carrying Value	$ 1,501	$ 0			$ 1,501
Redeemable Convertible Preferred Stock Series A, B, D, E-1, E-2, E-2A, E-3 and F
Temporary Equity [Line Items]
Shares Authorized (in shares)	9,640,493	0
Shares Issued (in shares)	9,456,775	0
Convertible preferred stock outstanding (in shares)	9,456,775	0			7,611,010
Original Issue Value	$ 45,321
Accumulated and Undeclared Dividends	12,249
Aggregate Liquidation Preference	57,570	$ 0
Carrying Value	$ 44,995	$ 0			$ 34,538
Series A
Temporary Equity [Line Items]
Shares Authorized (in shares)	533,711
Shares Issued (in shares)	533,711
Convertible preferred stock outstanding (in shares)	533,711
Original Issue Price per Share (in dollars per share)	$ 2.14
Original Issue Value	$ 1,142
Accumulated and Undeclared Dividends	713
Aggregate Liquidation Preference	1,856
Carrying Value	$ 1,142
Series B
Temporary Equity [Line Items]
Shares Authorized (in shares)	816,654
Shares Issued (in shares)	816,654
Convertible preferred stock outstanding (in shares)	816,654
Original Issue Price per Share (in dollars per share)	$ 2.25
Original Issue Value	$ 1,837
Accumulated and Undeclared Dividends	983
Aggregate Liquidation Preference	2,820
Carrying Value	$ 1,932
Series D
Temporary Equity [Line Items]
Shares Authorized (in shares)	756,416
Shares Issued (in shares)	756,416
Convertible preferred stock outstanding (in shares)	756,416
Original Issue Price per Share (in dollars per share)	$ 3.77
Original Issue Value	$ 2,852
Accumulated and Undeclared Dividends	1,340
Aggregate Liquidation Preference	4,191
Carrying Value	$ 2,852
Series E-1
Temporary Equity [Line Items]
Shares Authorized (in shares)	842,641
Shares Issued (in shares)	829,642
Convertible preferred stock outstanding (in shares)	829,642
Original Issue Price per Share (in dollars per share)	$ 3.77
Original Issue Value	$ 3,128
Accumulated and Undeclared Dividends	1,095
Aggregate Liquidation Preference	4,223
Carrying Value	$ 3,099
Series E-2
Temporary Equity [Line Items]
Shares Authorized (in shares)	949,725
Shares Issued (in shares)	934,433
Convertible preferred stock outstanding (in shares)	934,433
Original Issue Price per Share (in dollars per share)	$ 4.5776
Original Issue Value	$ 4,277
Accumulated and Undeclared Dividends	1,503
Aggregate Liquidation Preference	5,780
Carrying Value	$ 4,277
Series E-2A
Temporary Equity [Line Items]
Shares Authorized (in shares)	27,306
Shares Issued (in shares)	27,306
Convertible preferred stock outstanding (in shares)	27,306
Original Issue Price per Share (in dollars per share)	$ 4.5776
Original Issue Value	$ 125
Accumulated and Undeclared Dividends	39
Aggregate Liquidation Preference	164
Carrying Value	$ 125
Series E-3
Temporary Equity [Line Items]
Shares Authorized (in shares)	830,554
Shares Issued (in shares)	824,000
Convertible preferred stock outstanding (in shares)	824,000
Original Issue Price per Share (in dollars per share)	$ 5.3405
Original Issue Value	$ 4,401
Accumulated and Undeclared Dividends	1,364
Aggregate Liquidation Preference	5,764
Carrying Value	$ 4,394
Series F
Temporary Equity [Line Items]
Shares Authorized (in shares)	4,883,486
Shares Issued (in shares)	4,734,613
Convertible preferred stock outstanding (in shares)	4,734,613
Original Issue Price per Share (in dollars per share)	$ 5.8208			$ 5.8208
Original Issue Value	$ 27,559
Accumulated and Undeclared Dividends	5,212
Aggregate Liquidation Preference	32,772
Carrying Value	$ 27,174

Convertible Preferred Stock a_4

Convertible Preferred Stock and Preferred Stock Warrants - Narrative (Details)	Jul. 29, 2019shares	Jul. 11, 2019	Jun. 08, 2018USD ($)shares	May 31, 2018USD ($)shares	Jan. 12, 2018USD ($)$ / sharesshares	Dec. 31, 2019USD ($)installment$ / sharesshares	Dec. 31, 2017USD ($)shares	Dec. 31, 2018$ / sharesshares
Temporary Equity [Line Items]
Reverse stock split, conversion ratio		0.8203
Number of shares to be purchased by warrant (in shares)								403,142
Temporary equity, conversion multiplier		1.219
Convertible preferred stock outstanding (in shares)	9,973,884
Class of warrant or right, conversion multiplier	1.219	1.219
Convertible preferred stock, conversion threshold of IPO proceeds | $						$ 30,000,000
Number of years after issuance in which holders can request redemption						5 years
Number of equal annual installments company must redeem outstanding shares in | installment						3
Minimum notice holders must provide after redemption request						90 days
Common Stock
Temporary Equity [Line Items]
Conversion of convertible preferred stock (in shares)	8,181,992					8,181,992
Series F
Temporary Equity [Line Items]
Common stock issued and sold (in shares)			85,711	783,248	940,605		16,127
Proceeds from sale of stock | $			$ 499,000	$ 4,599,000	$ 5,475,000		$ 94,000
Convertible preferred stock, par value (in dollars per share) | $ / shares					$ 0.01
Temporary equity, fair value | $					$ 473,000
Convertible preferred stock outstanding (in shares)								4,734,613
Number of shares issued upon net warrants exercised (in shares)	27,207
Redeemable Convertible Preferred Stock Series A, B, D, E-1, E-2, E-2A, E-3 and F
Temporary Equity [Line Items]
Number of shares to be purchased by warrant (in shares)					67,233
Convertible preferred stock, par value (in dollars per share) | $ / shares						$ 0.001		$ 0.001
Convertible preferred stock outstanding (in shares)						0	7,611,010	9,456,775
Conversion of convertible preferred stock (in shares)						(9,470,828)

Convertible Preferred Stock a_5

Convertible Preferred Stock and Preferred Stock Warrants - Schedule of Preferred Stock Warrant Liabilities (Details)	Dec. 31, 2018$ / sharesshares
Class of Stock [Line Items]
Shares (in shares)	403,142
Exercised (in shares)	(219,243)
Expired (in shares)	(11,682)
Outstanding (in shares)	172,217
Series A
Class of Stock [Line Items]
Shares (in shares)	108,057
Exercise Price (in dollars per share) | $ / shares	$ 2.14
Exercised (in shares)	(96,375)
Expired (in shares)	(11,682)
Outstanding (in shares)	0
Series B
Class of Stock [Line Items]
Shares (in shares)	86,667
Exercise Price (in dollars per share) | $ / shares	$ 2.25
Exercised (in shares)	(86,667)
Expired (in shares)	0
Outstanding (in shares)	0
Series E-1
Class of Stock [Line Items]
Shares (in shares)	16,249
Exercise Price (in dollars per share) | $ / shares	$ 3.77
Exercised (in shares)	(3,250)
Expired (in shares)	0
Outstanding (in shares)	12,999
Series E-2
Class of Stock [Line Items]
Shares (in shares)	15,292
Exercise Price (in dollars per share) | $ / shares	$ 4.5776
Exercised (in shares)	0
Expired (in shares)	0
Outstanding (in shares)	15,292
Series E-3
Class of Stock [Line Items]
Shares (in shares)	6,554
Exercise Price (in dollars per share) | $ / shares	$ 5.3405
Exercised (in shares)	0
Expired (in shares)	0
Outstanding (in shares)	6,554
Series F Preferred Stock issued in 2016
Class of Stock [Line Items]
Shares (in shares)	103,090
Exercise Price (in dollars per share) | $ / shares	$ 5.8208
Exercised (in shares)	0
Expired (in shares)	0
Outstanding (in shares)	103,090
Series F Preferred Stock issued in 2018
Class of Stock [Line Items]
Shares (in shares)	67,233
Exercise Price (in dollars per share) | $ / shares	$ 0.01
Exercised (in shares)	(32,951)
Expired (in shares)	0
Outstanding (in shares)	34,282

Convertible Preferred Stock a_6

Convertible Preferred Stock and Preferred Stock Warrants - Schedule of Dividend Preferences and Rates (Details)	12 Months Ended
	Dec. 31, 2019$ / shares
Series F
Class of Stock [Line Items]
Annual dividend rate (in dollars per share)	$ 0.4657
Series E-3
Class of Stock [Line Items]
Annual dividend rate (in dollars per share)	0.4272
Series E-2A
Class of Stock [Line Items]
Annual dividend rate (in dollars per share)	0.3662
Series E-2
Class of Stock [Line Items]
Annual dividend rate (in dollars per share)	0.3662
Series E-1
Class of Stock [Line Items]
Annual dividend rate (in dollars per share)	0.3016
Series D
Class of Stock [Line Items]
Annual dividend rate (in dollars per share)	0.3016
Series C
Class of Stock [Line Items]
Annual dividend rate (in dollars per share)	0.2784
Series B
Class of Stock [Line Items]
Annual dividend rate (in dollars per share)	0.18
Series A
Class of Stock [Line Items]
Annual dividend rate (in dollars per share)	$ 0.1712

Stockholders' Equity (Deficit_2

Stockholders' Equity (Deficit) - Narrative (Details) $ / shares in Units, $ in Thousands	Jul. 29, 2019USD ($)$ / sharesshares	Jul. 12, 2019$ / sharesshares	Jul. 11, 2019	Dec. 31, 2019USD ($)vote$ / sharesshares	Dec. 31, 2018USD ($)$ / sharesshares
Class of Stock [Line Items]
Common stock, shares authorized (in shares)	200,000,000			200,000,000	15,102,000
Common stock, par value (in dollars per share) | $ / shares	$ 0.001			$ 0.001	$ 0.001
Number of votes per share | vote				1
Preferred stock, shares authorized (in shares)	10,000,000			10,000,000	0
Preferred stock, par value (in dollars per share) | $ / shares	$ 0.001			$ 0.001	$ 0.001
Common stock, dividends declared (in dollars per share) | $ / shares				0	0
Common stock, dividends paid (in dollars per share) | $ / shares				$ 0	$ 0
Reverse stock split, conversion ratio			0.8203
Number of shares to be purchased by warrant (in shares)					403,142
Proceeds from initial public offering of common stock, net of underwriting discounts, commissions and issuance costs | $	$ 65,900			$ 65,931	$ 0
Warrants Outstanding (in shares)					172,217
Common Stock
Class of Stock [Line Items]
Number of shares to be purchased by warrant (in shares)		209,243
Exercise price of warrants (in dollars per share) | $ / shares		$ 0.001
Initial percentage of shares exercisable		50.00%
Percentage of shares exercisable upon equity purchase requirement		50.00%
Warrants Outstanding (in shares)				244,480	0
IPO
Class of Stock [Line Items]
Common stock issued and sold (in shares)	4,600,000
Common stock offering price (in dollars per share) | $ / shares	$ 16
Over-Allotment Option
Class of Stock [Line Items]
Common stock issued and sold (in shares)	600,000

Stockholders' Equity (Deficit_3

Stockholders' Equity (Deficit) - Schedule of Common Stock Warrants Outstanding (Details) - $ / shares	Dec. 31, 2019	Jul. 12, 2019	Dec. 31, 2018
Class of Warrant or Right [Line Items]
Warrants Outstanding (in shares)			172,217
Common Stock
Class of Warrant or Right [Line Items]
Warrants Outstanding (in shares)	244,480		0
Exercise price of warrants (in dollars per share)		$ 0.001
July 12, 2026
Class of Warrant or Right [Line Items]
Warrants Outstanding (in shares)	209,243
Exercise price of warrants (in dollars per share)	$ 0.001
March 31, 2027
Class of Warrant or Right [Line Items]
Warrants Outstanding (in shares)	26,428
Exercise price of warrants (in dollars per share)	$ 7.10
November 30, 2028
Class of Warrant or Right [Line Items]
Warrants Outstanding (in shares)	8,809
Exercise price of warrants (in dollars per share)	$ 7.10

Stock Incentive Plans and Sto_3

Stock Incentive Plans and Stock Based Compensation - Activity Under Stock Incentive Plan (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Shares Available for Grant
Beginning balance (in shares)	458,726	551,918
Additional options authorized (in shares)	2,075,898	410,172
Granted (in shares)	(1,711,325)	(580,402)
Forfeited/Cancelled (in shares)	39,828	77,038
Ending balance (in shares)	863,127	458,726
Stock Options Outstanding
Beginning balance (in shares)	1,659,596	1,175,987
Granted (in shares)	1,711,325	580,402
Exercised (in shares)	(693,127)	(19,755)
Forfeited/Cancelled (in shares)	(39,828)	(77,038)
Ending balance (in shares)	2,637,966	1,659,596
Exercise Price
Beginning balance (in dollars per share)	$ 1.99	$ 1.79
Granted (in dollars per share)	19.41	2.39
Exercised (in dollars per share)	1.70	1.91
Forfeited/Cancelled (in dollars per share)	6.36	1.82
Ending balance (in dollars per share)	$ 13.30	$ 1.99
Stock Option Activity, Additional Disclosures
Options outstanding, weighted average remaining contractual term	8 years 7 months 20 days
Options outstanding, aggregate intrinsic value	$ 55,578
Options exercisable, number of options (in shares)	590,104
Options exercisable, weighted average exercise price (in dollars per share)	$ 2.20
Options exercisable, weighted average remaining contractual term	6 years 1 month 8 days
Options exercisable, aggregate intrinsic value	$ 18,984
Options outstanding, nonvested (in shares)	126,044
Options outstanding nonvested, weighted average exercise price (in dollars per share)	$ 2.39

Stock Incentive Plans and Sto_4

Stock Incentive Plans and Stock Based Compensation - Narrative (Details)	Feb. 14, 2020$ / sharesshares	Jan. 15, 2020$ / sharesshares	Jan. 01, 2020shares	Jul. 24, 2019shares	Jul. 11, 2019shares	Feb. 14, 2020	Dec. 31, 2019USD ($)purchase_period$ / sharesshares	Dec. 31, 2018USD ($)$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increase in number of shares authorized for issuance (in shares)							2,075,898	410,172
Number of options granted (in shares)							1,711,325	580,402
Exercise price of options granted (in dollars per share) | $ / shares							$ 19.41	$ 2.39
Options exercised, intrinsic value | $							$ 5,151,000	$ 0
Tax benefits related to stock-based compensation | $							$ 0	$ 0
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Term of awards							10 years
Percentage of share price at grant date							100.00%
Vesting period							4 years
Options granted, weighted average grant date fair value (in dollars per share) | $ / shares							$ 10.89	$ 1.35
Unrecognized compensation cost related to options | $							$ 18,417,000
Unrecognized compensation expense, period for recognition							3 years 4 months 20 days
ISOs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Term of awards							5 years
Percentage of voting power ownership							10.00%
Percentage of share price at grant date							110.00%
2018 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increase in number of shares authorized for issuance (in shares)					144,878
2019 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized for issuance (in shares)				1,931,020
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted, weighted average grant date fair value (in dollars per share) | $ / shares							$ 7.32	$ 0
Unrecognized compensation cost related to ESPP | $							$ 678,000
Employee stock purchase plan | Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized for issuance (in shares)							411,935
Number of offering periods | purchase_period							4
Purchase price of common stock, percentage of fair market value							85.00%
Offering period							24 months
Purchase period							6 months
Employee stock purchase plan | Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense, period for recognition							1 year 6 months 20 days
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increase in number of shares authorized for issuance (in shares)				1,976,756
First Year of Vesting | Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period							1 year
Vesting percentage							25.00%
Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options granted (in shares)	135,000	17,500
Exercise price of options granted (in dollars per share) | $ / shares	$ 31.80	$ 31.97
Subsequent Event | Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Term of awards						10 years
Vesting period						4 years
Subsequent Event | 2019 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increase in number of shares authorized for issuance (in shares)			856,545
Subsequent Event | Employee stock purchase plan | Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increase in number of shares authorized for issuance (in shares)			171,309
Subsequent Event | First Year of Vesting | Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period						1 year
Vesting percentage						25.00%
Subsequent Event | Last Three Years of Vesting | Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period						36 months

Stock Incentive Plans and Sto_5

Stock Incentive Plans and Stock Based Compensation - Assumptions Used in Fair Value of Stock Options and ESPP (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Average expected term (years)	6 years	6 years
Expected stock price volatility, minimum	56.74%	57.77%
Expected stock price volatility, maximum	60.17%	58.29%
Risk-free interest rate, minimum	1.63%	2.77%
Risk-free interest rate, maximum	2.47%	3.13%
Dividend yield	0.00%	0.00%
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Average expected term (years)	1 year 1 month 28 days
Expected stock price volatility, minimum	61.12%
Expected stock price volatility, maximum	68.89%
Risk-free interest rate, minimum	1.56%
Risk-free interest rate, maximum	1.80%
Dividend yield	0.00%

Stock Incentive Plans and Sto_6

Stock Incentive Plans and Stock Based Compensation - Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 1,249	$ 294
Cost of sales
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	170	24
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	165	56
Selling, general and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 914	$ 214

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Operating Loss Carryforwards [Line Items]
Deferred tax assets, valuation allowance	$ 12,420	$ 14,375
Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	57,429
NOL carryforwards, subject to expiration	43,536
NOL carryforwards, not subject to expiration	13,893
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 42,211

Income Taxes - Components of In

Income Taxes - Components of Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Current tax expense
U.S. Federal	$ 0	$ 0
State and local	72	9
Total current	72	9
Deferred tax expense
U.S. Federal	0	0
State and local	0	0
Total deferred	0	0
Total income tax expense	$ 72	$ 9

Income Taxes - Income Tax Expen

Income Taxes - Income Tax Expense Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Pre-tax income (loss)	$ 5,349	$ (6,358)
U.S. federal taxes at statutory rate	1,123	(1,335)
State income taxes	958	(1,174)
Mark-to-market losses	566	57
Non-deductible meals	224	119
Convertible debt interest	95	0
Research and development (“R&D”) tax credit	(251)	0
Change in valuation allowance	(2,747)	2,278
Stock-based compensation	65	53
Other	39	11
Total income tax expense	$ 72	$ 9

Income Taxes - Deferred Tax Ass

Income Taxes - Deferred Tax Assets And Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Net operating loss (“NOL”) carryforwards	$ 14,077	$ 16,184
Accounts payable	456	390
Accrued liabilities	1,817	1,432
R&D tax credit	993	715
Intangible assets	50	61
Stock-based compensation	127	12
Charitable contributions	2	4
Total deferred tax assets	17,522	18,798
Less valuation allowance	(12,420)	(14,375)
Deferred tax assets, net	5,102	4,423
Deferred tax liabilities:
Accounts receivable	(3,796)	(3,249)
Prepaid expenses	(757)	(378)
Property and equipment	(246)	(131)
Section 481(a) adjustment (cash to accrual)	(303)	(665)
Total deferred tax liabilities	(5,102)	(4,423)
Net deferred tax asset (liability)	$ 0	$ 0

Selected Quarterly Financial _3

Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
NET REVENUES	$ 17,635	$ 14,774	$ 10,739	$ 8,717	$ 11,436	$ 3,712	$ 3,979	$ 3,659	$ 51,865	$ 22,786
Gross margin	15,624	13,066	8,746	7,119	10,070	2,361	2,652	2,406	44,555	17,489
Net income (loss)	2,055	5,849	(1,269)	(1,358)	3,868	(3,450)	(3,155)	(3,630)	5,277	(6,367)
Net income (loss) attributable to common stockholders	$ 2,055	$ 5,543	$ (2,265)	$ (2,342)	$ 2,862	$ (4,456)	$ (4,080)	$ (4,489)	$ 2,991	$ (10,163)
Earnings (loss) per share
Basic (in dollars per share)	$ 0.12	$ 0.43	$ (1.05)	$ (1.22)	$ 1.49	$ (2.33)	$ (2.15)	$ (2.37)	$ 0.35	$ (5.33)
Diluted (in dollars per share)	$ 0.11	$ 0.05	$ (1.05)	$ (1.22)	$ 0.38	$ (2.33)	$ (2.15)	$ (2.37)	$ (0.21)	$ (5.33)
Gain on extinguishment of debt (Note 7)		$ 5,213							$ 5,213	$ 0
Revenue recognized due to release of constraint on variable consideration					$ 5,191

Subsequent Events (Details)

Subsequent Events (Details) - $ / shares	Feb. 28, 2020	Feb. 14, 2020	Jan. 15, 2020	Feb. 14, 2020	Dec. 31, 2019	Dec. 31, 2018
Subsequent Event [Line Items]
Number of options granted (in shares)					1,711,325	580,402
Exercise price of options granted (in dollars per share)					$ 19.41	$ 2.39
Subsequent Event
Subsequent Event [Line Items]
Number of options granted (in shares)		135,000	17,500
Exercise price of options granted (in dollars per share)		$ 31.80	$ 31.97
Employee stock purchase plan | Subsequent Event
Subsequent Event [Line Items]
Shares issued during period (in shares)	39,987
Shares issued during period, weighted average price per share (in dollars per share)	$ 15.09
Stock options
Subsequent Event [Line Items]
Term of awards					10 years
Vesting period					4 years
Stock options | Subsequent Event
Subsequent Event [Line Items]
Term of awards				10 years
Vesting period				4 years
First Year of Vesting | Stock options
Subsequent Event [Line Items]
Vesting period					1 year
Vesting percentage					25.00%
First Year of Vesting | Stock options | Subsequent Event
Subsequent Event [Line Items]
Vesting period				1 year
Vesting percentage				25.00%
Last Three Years of Vesting | Stock options | Subsequent Event
Subsequent Event [Line Items]
Vesting period				36 months