Summary of Significant Accounting Policies | 3. Summary of Significant Accounting Policies Basis of Presentation The accompanying financial statements and notes are prepared in accordance with accounting principles generally accepted in the United States of America, or U.S. GAAP, and are prepared on the basis that the Company will continue as a going concern (see Note 2). The accompanying financial statements and notes do not include any adjustments to reflect the possible future effects on the recoverability and classification of assets or the amounts and classification of liabilities that may result from the possible inability of the Company to continue as a going concern. On July 6, 2018, the Company’s stockholders approved, and the Company filed, an amendment to the Company’s Certificate of Amendment of Certificate of Incorporation to effect a one-for-thirty reverse stock split of the Company’s outstanding common stock. As such, all references to share and per share amounts in these financial statements and accompanying notes have been retroactively restated to reflect the one-for-thirty reverse stock split, except for the authorized number of shares of the Company’s common stock of 150,000,000 shares, which was not affected by the one-for-thirty reverse stock split. Going Concern The Company assesses and determines its ability to continue as a going concern in accordance with the provisions of ASC Topic 205-40, Presentation of Financial Statements—Going Concern, which requires the Company to evaluate whether there are conditions or events that raise substantial doubt about its ability to continue as a going concern within one year after the date that its annual and interim financial statements are issued (see Note 2). Certain additional financial statement disclosures are required if such conditions or events are identified. If and when an entity’s liquidation becomes imminent, financial statements should be prepared under the liquidation basis of accounting. Determining the extent, if any, to which conditions or events raise substantial doubt about the Company’s ability to continue as a going concern, or the extent to which mitigating plans sufficiently alleviate any such substantial doubt, as well as whether or not liquidation is imminent, requires significant judgment by management. Use of Estimates The preparation of financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. On an ongoing basis, management evaluates these estimates and judgments, including those related to accounts receivable, inventories, long-lived assets, income taxes, revenues, stock-based compensation, and the determination of the Company’s ability to continue as a going concern. The Company bases its estimates on various assumptions that it believes are reasonable under the circumstances. Actual results may differ from these estimates under different assumptions or conditions. Revenue Recognition and Accounts Receivable The Company's commercial revenues are generated from diagnostic services provided to patient’s physicians and billed to third-party insurance payers such as managed care organizations, Medicare and Medicaid and patients for any deductibles, coinsurance or copayments that may be due. Commencing on March 31, 2017, the Company began to recognize commercial revenue related to billings for assays delivered and billed to Medicare and other third-party payers on an accrual basis when amounts that will ultimately be realized can be estimated upon delivery, whereby prior to March 31, 2017, the Company recognized revenues for its commercial diagnostic services on a cash basis as collected because the amounts ultimately expected to be received could not be estimated upon delivery due to insufficient collection history experience. Commencing on January 1, 2018, the Company recognizes revenue in accordance with ASC 606, Revenue from Contracts with Customers, or ASC 606, which requires that an entity recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled to in exchange for those goods or services. The Company adopted the provisions of ASC 606 using the modified retrospective application method applied to all contracts, which did not impact amounts previously reported by the Company, nor did it require a cumulative effect adjustment upon adoption, as the Company’s method of recognizing revenue under ASC 606 was analogous to the method utilized immediately prior to adoption. Accordingly, there is no need for the Company to disclose the amount by which each financial statement line item was affected as a result of applying the new standard and an explanation of significant changes. Contracts For its commercial revenues, while the Company markets directly to physicians, its customer is the patient. Patients do not enter into direct agreements with the Company that commit either them to pay any portion of the cost of the tests if they have not met their annual deductible limit under their insurance policy, if any, or if their insurance otherwise declines to reimburse the Company. Accordingly, the Company establishes a contract with a commercial patient in accordance with other customary business practices, as follows: • Approval of a contract is established via the order and accession, which are submitted by the patient’s physician. • The Company is obligated to perform its diagnostic services upon receipt of a sample from a physician, and the patient and/or applicable payer are obligated to reimburse the Company for services rendered based on the patient’s insurance benefits. • Payment terms are a function of a patient’s existing insurance benefits, including the impact of coverage decisions with CMS and applicable reimbursement contracts established between the Company and payers, unless the patient is a self-pay patient, whereby the Company bills the patient directly after the services are provided. • Once the Company delivers a patient’s assay result to the ordering physician, the contract with a patient has commercial substance, as the Company is legally able to collect payment and bill an insurer and/or patient, regardless of payer contract status or patient insurance benefit status. • Consideration associated with commercial revenues is considered variable and constrained until fully adjudicated, with net revenues recorded to the extent that it is probable that a significant reversal will not occur. The Company’s development services revenues are supported by contractual agreements and generated from assay development services provided to entities, as well as certain other diagnostic services provided to physicians, and revenues are recognized upon delivery of the performance obligations in the contract. Performance Obligations A performance obligation is a promise in a contract to transfer a distinct good or service, or a bundle of goods or services, to the customer. For its commercial and development services revenues, the Company’s contracts have a single performance obligation, which is satisfied upon rendering of services, which culminates in the delivery of a patient’s assay result(s) to the ordering physician or entity. The duration of time between accession receipt and delivery of a valid assay result to the ordering physician or entity is typically less than two weeks. Accordingly, the Company elected the practical expedient and therefore, does not disclose the value of unsatisfied performance obligations. Transaction Price The transaction price is the amount of consideration that the Company expects to collect in exchange for transferring promised goods or services to a customer, excluding amounts collected on behalf of third parties, such as sales taxes. The consideration expected from a contract with a customer may include fixed amounts, variable amounts, or both. The Company’s gross commercial revenues billed, and corresponding gross accounts receivable, are subject to estimated deductions for such allowances and reserves to arrive at reported net revenues, which relate to differences between amounts billed and corresponding amounts estimated to be subsequently collected and is deemed to be variable although the variability is not explicitly stated in any contract. Rather, the implied variability is due to several factors, such as the payment history or lack thereof for third-party payers, reimbursement rate changes for contracted and non-contracted payers, any patient co-payments, deductibles or compliance incentives, the existence of secondary payers and claim denials. The Company estimates the amount of variable consideration using the most likely amount approach to estimating variable consideration for third-party payers, including direct patient bills, whereby the estimated reimbursement for services are established by payment histories on CPT codes for each payer, or similar payer types. When no payment history is available, the value of the account is estimated at Medicare rates, with additional other payer-specific reserves taken as appropriate. Collection periods for billings on commercial revenues range from less than 30 days to several months, depending on the contracted or non-contracted nature of the payer, among other variables. The estimates of amounts that will ultimately be realized from commercial diagnostic services for non-contracted payers require significant judgment by management. The Company limits the amount of variable consideration included in the transaction price to the unconstrained portion of such consideration. Revenue is recognized up to the amount of variable consideration that is not subject to a significant reversal until additional information is obtained or the uncertainty associated with the additional payments or refunds is subsequently resolved. Differences between original estimates and subsequent revisions, including final settlements, represent changes in the estimate of variable consideration and are included in the period in which such revisions are made. The Company monitors its estimates of transaction price to depict conditions that exist at each reporting date. If the Company subsequently determines that it will collect more consideration than it originally estimated for a contract with a customer, it will account for the change as an increase in the estimate of the transaction price in the period identified as an increase to revenue. Similarly, if the Company subsequently determines that the amount it expects to collect from a customer is less than it originally estimated, it will generally account for the change as a decrease in the estimate of the transaction price as a decrease to revenue, provided that such downward adjustment does not result in a significant reversal of cumulative revenue recognized. Revenue recognized from changes in transaction prices was not significant during the year ended December 31, 2018. Allocate Transaction Price For the Company’s commercial revenues, the entire transaction price is allocated to the single performance obligation contained in a contract with a customer. For the Company’s development services revenues, the contracted transaction price is allocated to each single performance obligation contained in a contract with a customer as performed. Point-in-time Recognition The Company’s single performance obligation is satisfied at a point in time, and that point in time is defined as the date a patient’s successful assay result is delivered to the patient’s ordering physician or entity. The Company considers this date to be the time at which the patient obtains control of the promised diagnostic assay service. Contract Balances The timing of revenue recognition, billings and cash collections results in accounts receivable recorded in the Company’s condensed balance sheets. Generally, billing occurs subsequent to delivery of a patient’s test result to the ordering physician or entity, resulting in an account receivable. Practical Expedients The Company does not adjust the transaction price for the effects of a significant financing component, as at contract inception, the Company expects the collection cycle to be one year or less. The Company expenses sales commissions when incurred because the amortization period is one year or less, which are recorded within sales and marketing expenses. The Company incurs certain other costs that are incurred regardless of whether a contract is obtained. Such costs are primarily related to legal services and patient communications. These costs are expensed as incurred and recorded within general and administrative expenses. Disaggregation of Revenue and Concentration of Risk The composition of the Company’s net revenues recognized during the years ended December 31, 2017 and 2018, disaggregated by source and nature, are as follows: For the year ended December 31, 2017 2018 Net revenues from contracted payers* $ 2,074,596 $ 1,348,383 Net revenues from non-contracted payers 2,721,717 1,703,179 Development services revenues 272,350 198,736 Total net revenues $ 5,068,663 $ 3,250,298 *Includes Medicare and Medicare Advantage, as reimbursement amounts are fixed and miscellaneous income from CEE-Sure blood collection tubes. For the year ended December 31, 2017 2018 Net commercial revenues recognized upon delivery $ 3,570,337 $ 3,051,562 Development services revenues recognized upon delivery 272,350 198,736 Commercial revenues recognized upon cash collection 1,225,976 — Total net revenues $ 5,068,663 $ 3,250,298 The amount of nonrecurring net revenue recorded during the year ended December 31, 2017, had the Company commenced recognizing revenue for commercial diagnostic services upon delivery on or prior to December 31, 2016 instead of on March 31, 2017, was $843,000, and the corresponding decrease in net loss per common share was $0.90. The incremental net revenue and decrease in loss from operations as a result of recognizing revenue on an accrual basis commencing on March 31, 2017, or the total amount of net revenue recorded in excess of the amount of commercial cash collections, was $1,139,000 during the year ended December 31, 2017, and the corresponding decrease in net loss per common share was $1.20, respectively. For the year ended December 31, 2018 all revenues were recognized on an accrual basis. Concentrations of credit risk with respect to revenues are primarily limited to geographies to which the Company provides a significant volume of its services, and to specific third-party payers of the Company’s services such as Medicare, insurance companies, and other third-party payers. The Company’s client base consists of many geographically dispersed clients diversified across various customer types. The composition of the Company’s gross and net revenues recognized during the years ended December 31, 2017 and 2018 is as follows: For the year ended December 31, 2017 2018 Commercial revenues recognized upon delivery $ 15,685,069 $ 12,505,149 Development services revenues recognized upon delivery 272,350 198,736 Commercial revenues recognized upon cash collection 1,225,976 — Total gross revenues 17,183,395 12,703,885 Provisions for contractual discounts (5,805,787 ) (3,937,993 ) Provisions for aged non-patient receivables (735,709 ) (326,137 ) Provisions for estimated patient receivables (169,479 ) (66,470 ) Provisions for other payer-specific sales allowances (5,403,757 ) (5,122,987 ) Net revenues $ 5,068,663 $ 3,250,298 A summary of activity in the Company’s gross and net accounts receivable balances, as well as corresponding reserves, during the year ended December 31, 2018 is as follows: Balance at Amounts Settlements Balance at December 31, Recognized Upon December 31, 2017 Upon Delivery Adjudication 2018 Accounts receivable, gross $ 6,937,063 $ 12,835,371 $ (11,889,832 ) $ 7,882,602 Reserve for contractual discounts (1,974,849 ) (3,214,615 ) 3,011,989 (2,177,475 ) Reserve for aged non-patient receivables (452,088 ) (994,542 ) 880,682 (565,948 ) Reserve for estimated patient receivables (88,120 ) (135,955 ) 208,598 (15,477 ) Reserve for other payer-specific sales allowances (3,228,580 ) (5,239,961 ) 4,919,164 (3,549,377 ) Accounts receivable, net $ 1,193,426 $ 3,250,298 $ (2,869,399 ) $ 1,574,325 Cash The Company places its cash with reputable financial institutions that are insured by the Federal Deposit Insurance Corporation, or FDIC. At times, deposits held may exceed the amount of insurance provided by the FDIC. The Company has not experienced any losses in its cash and believes they are not exposed to any significant credit risk. Fair Value Measurements The Company uses a three-tier fair value hierarchy to prioritize the inputs used in the Company’s fair value measurements. These tiers include: Level 1, defined as observable inputs such as quoted prices in active markets for identical assets; Level 2, defined as inputs other than quoted prices in active markets that are either directly or indirectly observable; and Level 3, defined as unobservable inputs in which little or no market data exists, therefore requiring an entity to develop its own assumptions. The Company believes the carrying amount of cash, accounts receivable, accounts payable and accrued expenses approximate their estimated fair values due to the short-term maturities of these financial instruments. See Note 5 for further details about the inputs and assumptions used to determine fair value measurements. Concentration of Risk Financial instruments that potentially subject the Company to concentrations of credit risk consist principally of temporary cash investments. Concentrations of credit risk with respect to revenues are primarily limited to geographies to which the Company provides a significant volume of its services, and to specific third-party payers of the Company’s services such as Medicare, insurance companies, and other third-party payers. The Company’s client base consists of a large number of geographically dispersed clients diversified across various customer types. The Company's third-party payers that represent more than 10% of total net revenues in any period presented, as well as their related net revenue amount as a percentage of total net revenues, during the years ended December 31, 2017 and 2018 were as follows: For the year ended December 31, 2017 2018 Medicare and Medicare Advantage 39 % 39 % Blue Cross Blue Shield 19 % 11 % United Healthcare 12 % 17 % The Company's third-party payers that represent more than 10% of total net accounts receivable, and their related net accounts receivable balance as a percentage of total net accounts receivable, at December 31, 2017 and 2018 were as follows: For the year ended December 31, 2017 2018 Blue Cross Blue Shield 27 % 22 % Medicare and Medicare Advantage 21 % 17 % United Healthcare 15 % 15 % The Company operates in one reportable business segment and historically has derived most revenues only from within the United States. Certain components used in the Company’s current or planned products are currently sourced from one supplier, for which alternative suppliers exist but the Company has not validated the product(s) of such alternative supplier(s), and substitutes for these components may not be obtained easily or may require substantial design or manufacturing modifications. Inventories Inventories are valued at the lower of cost or net realizable value. Cost is determined by the average cost method. The Company records adjustments to its inventory for estimated obsolescence or diminution in net realizable value equal to the difference between the cost of the inventory and the estimated net realizable value. At the point of loss recognition, a new cost basis for that inventory is established, and subsequent changes in facts and circumstances do not result in the restoration or increase in that newly established cost basis. In addition, the Company records a liability for firm, non-cancelable, and unconditional purchase commitments with contract manufacturers and suppliers for quantities in excess of the Company’s future demand forecasts consistent with its valuation of excess and obsolete inventory. Fixed Assets Fixed assets consist of machinery and equipment, furniture and fixtures, computer equipment and software, leasehold improvements, financed equipment and construction in-process. Fixed assets are stated at cost less accumulated depreciation and amortization. Additions, improvements, and major renewals are capitalized. Maintenance, repairs, and minor renewals are expensed as incurred. Depreciation and amortization are recorded using the straight-line method over the estimated useful lives of the assets, which range from three to seven years. Leasehold improvements are amortized over the life of the lease or the asset, whichever is shorter. Depreciation and amortization expense for the years ended December 31, 2017 and 2018 was approximately $576,000 and $801,000, respectively. Upon sale or disposal of fixed assets, the accounts are relieved of the cost and the related accumulated depreciation or amortization with any gain or loss recorded to the statement of operations and comprehensive loss. Fixed assets are reviewed for impairment whenever changes in circumstances indicate that the carrying amount of an asset may not be recoverable. These computations utilize judgments and assumptions inherent in the estimates of future cash flows to determine recoverability of these assets. If the assumptions about these assets were to change as a result of events or circumstances, the Company may be required to record an impairment loss. Stock-based Compensation The Company measures and recognizes compensation expense for all stock-based awards made to employees and directors based on their grant date fair values. The Company estimates the fair value of stock option awards on the date of grant using the Black-Scholes option pricing model, while the fair value of restricted stock unit awards, or RSUs, is determined by the Company’s stock price on the date of grant. The value of the portion of the award that is ultimately expected to vest is recognized as expense over the requisite service periods using the straight-line method. In addition, the Company estimates forfeitures at the time of grant and revises these estimates in subsequent periods if actual forfeitures differ from those estimates (see Note 10). The Company determines the fair value of the stock-based compensation awards granted as either the fair value of the consideration received, or the fair value of the equity instruments issued, whichever is more reliably measurable. All issuances of equity instruments issued to non-employees as consideration for goods or services received by the Company are accounted for based on the fair value of the equity instruments issued. These awards are recorded in expense and additional paid-in capital in shareholders’ equity over the applicable service periods based on the fair value of the options at the end of each period. Calculating the fair value of stock-based awards requires the input of highly subjective assumptions into the Black-Scholes valuation model. Stock-based compensation expense is calculated using the Company’s best estimates, which involves inherent uncertainties, and the application of management’s judgment. Significant estimates include the expected life of the stock option, stock price volatility and risk-free interest rate. Research and Development Research and development costs are expensed as incurred. The amounts expensed in the years ended December 31, 2017 and 2018 were approximately $3,365,000 and $4,469,000, respectively, which includes salaries of research and development personnel. Income Taxes The Company provides for income taxes utilizing the liability method. Under the liability method, current income tax expense or benefit is the amount of income taxes expected to be payable or refundable for the current year. A deferred income tax asset or liability is computed for the expected future impact of differences between the financial reporting and tax bases of assets and liabilities and for the expected future tax benefit to be derived from tax credits. Tax rate changes are reflected in the computation of the income tax provision during the period such changes are enacted. Deferred tax assets are reduced by a valuation allowance when, in management’s opinion, it is more likely than not that some portion or all of the deferred tax assets will not be realized. The Company considers the scheduled reversal of deferred tax liabilities, projected future taxable income, and tax planning strategies in making this assessment. The Company’s valuation allowance is based on available evidence, including its current year operating loss, evaluation of positive and negative evidence with respect to certain specific deferred tax assets including evaluation sources of future taxable income to support the realization of the deferred tax assets. The Company has established a full valuation allowance on the deferred tax assets as of December 31, 2017 and 2018, and therefore has not recognized any income tax benefit or expense in the periods presented. A tax benefit from uncertain tax positions may be recognized by the Company when it is more-likely-than-not that the position will be sustained upon examination, including resolutions of any related appeals or litigation processes, based on the technical merits of the position. Income tax positions must meet a more-likely-than-not recognition threshold to be recognized. The Company recognizes interest and/or penalties related to income tax matters in income tax expense. There is no accrual for interest or penalties for income taxes on the balance sheets at December 31, 2017 and 2018, and the Company has not recognized interest and/or penalties in the statements of operations and comprehensive loss for the years ended December 31, 2017 and 2018. Recent Accounting Pronouncements In January 2016, the FASB issued authoritative guidance requiring, among other things, that certain equity investments be measured at fair value with changes in fair value recognized in net income, that financial assets and financial liabilities be presented separately by measurement category and form of financial asset on the balance sheet or the accompanying notes to the financial statements, that the prior requirement to disclose the method(s) and significant assumptions used to estimate the fair value that is required to be disclosed for financial instruments measured at amortized cost on the balance sheet be eliminated, and that a reporting organization is to present separately in other comprehensive income the portion of the total change in the fair value of a liability resulting from a change in the instrument-specific credit risk when the organization has elected to measure the liability at fair value in accordance with the fair value option for financial instruments. This guidance is effective for fiscal years, and interim periods within those years, beginning after December 15, 2017. Early adoption of the instrument-specific credit risk amendment is permitted. The Company adopted this guidance for the fiscal year beginning on January 1, 2018, which did not have a material impact on its financial statements or disclosures. In February 2016, the FASB issued authoritative guidance the Company will elect the optional transition method to account for the impact of the adoption with a cumulative-effect adjustment in the period of adoption and will not restate prior periods. The Company expects to elect certain practical expedients permitted under the transition guidance. The Company will record a right-of-use asset and liability upon adoption of the guidance. The Company is currently finalizing its review of contracts and may identify additional embedded leases and additional amounts to be recorded . In August 2016, the FASB issued authoritative guidance clarifying the classification of certain cash receipts and cash payments in the statement of cash flows. This guidance is effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years, on a retrospective transition method to each period presented. Early adoption is permitted. The Company adopted this guidance for the reporting period beginning January 1, 2018, which did not have a material impact on its financial statements or disclosures. In January 2017, the FASB issued authoritative guidance clarifying the definition of a business when evaluating transactions involving acquisitions or disposals of assets or businesses. This guidance is effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. Certain applications of this guidance are permitted for early adoption. The Company adopted this guidance for the reporting period beginning January 1, 2018, which did not have a material impact on its financial statements or disclosures. In July 2017, the FASB issued authoritative guidance changing the classification analysis of certain equity-linked financial instruments (or embedded features) with down round features, whereby a down round feature no longer precludes equity classification when assessing whether the instrument is indexed to an entity’s own stock, and also clarifying existing disclosure requirements for equity-classified instruments. This guidance is effective for fiscal years beginning after December 15, 2019, and interim periods within fiscal years beginning after December 15, 2020. Early adoption is permitted. The Company early adopted this guidance for the fiscal year beginning on January 1, 2018, which did not have a material impact on its financial statements or disclosures upon adoption, but did result in equity classification for the warrants issued on January 30, 2018, whereby liability classification may have occurred in the absence of the adoption of this guidance due to the existence of a down round feature associated with the exercise price of the warrants, which would have resulted in material impacts to the Company’s financial statements and disclosures. In August 2017, the FASB issued authoritative guidance that expands and refines hedge accounting for both nonfinancial and financial risk components and align the recognition and presentation of the effects of the hedging instrument and the hedged item in the financial statements. This guidance is effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Early application is permitted. The Company adopted this guidance for the fiscal year beginning on January 1, 2019 and determined that the adoption of this guidance not will have a material impact on its financial statements or disclosures because the Company does not currently hold any financial instruments accounted for as a hedging activity. In February 2018, the FASB issued authoritative guidance allowing a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from a tax bill, “H.R.1, An Act to Provide for Reconciliation Pursuant to Titles II and V of the Concurrent Resolution on the Budget for Fiscal Year 2018,” or the Tax Cuts and Jobs Act, enacted on December 22, 2017. These amendments eliminate the stranded tax effects resulting from the Tax Cuts and Jobs Act. However, because these amendments only relate to the reclassification of the income tax effects of the Tax Cuts and Jobs Act, the underlying guidance that requires that the effect of a change in tax laws or rates be included in income from continuing operations is not affected. This guidance also requires certain disclosures about stranded tax effects. This guidance is effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Early adoption is permitted. The Company adopted this guidance for the fiscal year beginning on January 1, 2019 and determined that the adoption of this guidance will not have a material impact on its financial statements or disclosures because the Company does not currently maintain any stranded tax effects in accumulated other comprehensive income. In February 2018, the FASB issued authoritative guidance concerning certain fair value option liabilities, equity securities without a readily determinable fair value |