CareDx (CDNA) 10-Q 14 Nov 14 2014 Q3 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	9 Months Ended
	Sep. 30, 2014	Nov. 11, 2014
Document And Entity Information [Abstract]	'	'
Document Type	'10-Q	'
Amendment Flag	'false	'
Document Period End Date	30-Sep-14	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q3	'
Trading Symbol	'CDNA	'
Entity Registrant Name	'CareDx, Inc.	'
Entity Central Index Key	'0001217234	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Non-accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	11,803,484

Consolidated_Condensed_Balance

Consolidated Condensed Balance Sheets (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Current assets:	'	'
Cash and cash equivalents	$39,048	$5,128
Accounts receivable	1,749	2,270
Inventory	496	518
Prepaid and other assets	718	255
Total current assets	42,011	8,171
Property and equipment, net	2,049	1,553
Intangible assets, net	6,650	0
Goodwill	12,005	0
Restricted cash	147	147
Other noncurrent assets	0	2
Total assets	62,862	9,873
Current liabilities:	'	'
Accounts payable	1,036	618
Accrued payroll liabilities	1,403	1,386
Accrued and other liabilities	1,911	1,048
Accrued royalties	297	0
Deferred revenue	673	80
Current portion of long-term debt	5,798	4,461
Total current liabilities	11,118	7,593
Accrued royalties	0	2,804
Deferred rent, net of current portion	1,734	1,885
Deferred revenue, net of current portion	1,004	1,623
Long-term debt, net of current portion	6,930	10,914
Convertible preferred stock warrant liability	0	525
Contingent consideration	1,037	0
Total liabilities	21,823	25,344
Commitments and contingencies (Note 7)	'	'
Convertible preferred stock: $0.001 par value; 0 and 6,417,954 shares authorized at September 30, 2014 and December 31, 2013, respectively; 0 and 5,155,673 shares issued and outstanding at September 30, 2014 and December 31, 2013, respectively; liquidation value of $0 and $137,221 at September 30, 2014 and December 31, 2013, respectively	0	135,202
Stockholders' equity (deficit):	'	'
Preferred stock: $0.001 par value; 10,000,000 and 0 shares authorized at September 30, 2014 and December 31, 2013, respectively; 0 and 0 shares issued and outstanding at September 30, 2014 and December 31, 2013, respectively	'	'
Common stock: $0.001 par value; 100,000,000 and 7,737,226 shares authorized at September 30, 2014 and December 31, 2013, respectively; 11,792,746 and 1,010,711 shares issued and outstanding at September 30, 2014 and December 31, 2013, respectively	12	1
Additional paid-in capital	200,397	9,482
Accumulated deficit	-159,370	-160,156
Total stockholders' equity (deficit)	41,039	-150,673
Total liabilities, convertible preferred stock and stockholders' equity (deficit)	$62,862	$9,873

Consolidated_Condensed_Balance1

Consolidated Condensed Balance Sheets (Parenthetical) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, except Share data, unless otherwise specified
Statement of Financial Position [Abstract]	'	'
Convertible preferred stock, par value	$0.00	$0.00
Convertible preferred stock, shares authorized	0	6,417,954
Convertible preferred stock, shares issued	0	5,155,673
Convertible preferred stock, shares outstanding	0	5,155,673
Convertible preferred stock, liquidation	$0	$137,221
Preferred stock, par value	$0.00	$0.00
Preferred stock, shares authorized	10,000,000	0
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$0.00	$0.00
Common stock, shares authorized	100,000,000	7,737,226
Common stock, shares issued	11,792,746	1,010,711
Common stock, shares outstanding	11,792,746	1,010,711

Consolidated_Condensed_Stateme

Consolidated Condensed Statements of Operations (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Revenue:	'	'	'	'
Testing revenue	$6,601	$5,714	$19,145	$15,856
Collaboration and license revenue	53	91	209	387
Total revenue	6,654	5,805	19,354	16,243
Operating expenses:	'	'	'	'
Cost of testing	1,772	2,502	6,337	6,745
Research and development	1,036	668	2,548	2,516
Sales and marketing	1,753	1,452	4,837	4,569
General and administrative	1,976	1,515	6,087	3,779
Change in estimated fair value of contingent consideration	-1,276	0	-1,276	0
Total operating expenses	5,261	6,137	18,533	17,609
Income (loss) from operations	1,393	-332	821	-1,366
Interest expense, net	-535	-497	-1,727	-1,603
Other income (expense), net	355	-1	192	-11
Income (loss) before income taxes	1,213	-830	-714	-2,980
Income tax benefit	0	0	1,500	0
Net income (loss)	$1,213	($830)	$786	($2,980)
Net income (loss) per share (Note 3):	'	'	'	'
Basic	$0.13	($0.82)	$0.21	($2.95)
Diluted	$0.12	($0.82)	$0.11	($2.95)
Shares used to compute net income (loss) per share:	'	'	'	'
Basic	9,279,649	1,011,136	3,798,559	1,011,001
Diluted	11,219,377	1,011,136	8,298,903	1,011,001

Consolidated_Condensed_Stateme1

Consolidated Condensed Statements of Cash Flows (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
Operating activities	'	'
Net income (loss)	$786	($2,980)
Adjustments to reconcile net income (loss) to net cash (used in) provided by operating activities:	'	'
Depreciation and amortization	354	540
Stock-based compensation	350	57
Amortization of deferred revenue	-26	-172
Accretion of debt discount and noncash interest expense	792	407
Change in fair value of warrants	14	0
Change in fair value of embedded derivative	-239	0
Change in estimated fair value of contingent consideration	-1,276	0
Non-cash income tax benefit	-1,500	0
Changes in operating assets and liabilities:	'	'
Accounts receivable	521	-341
Inventory	22	32
Prepaid expenses and other assets	-461	42
Accounts payable	204	754
Accrued payroll liabilities	17	178
Accrued royalties	-2,507	920
Deferred revenue	0	1,083
Accrued and other liabilities	321	-148
Net cash (used in) provided by operating activities	-2,628	372
Investing activities	'	'
Payment for acquisitions, net of cash acquired	-406	0
Purchase of property and equipment	-333	-60
Net cash used in investing activities	-739	-60
Financing activities	'	'
Proceeds from initial public offering, net of underwriters discount	39,246	0
Payment of initial public offering costs	-3,716	0
Proceeds from subordinated convertible debt, net of issuance costs	4,982	0
Repayment of capital lease obligations	-55	-45
Issuance costs in connection with loan modification	0	-6
Principal payments on debt	-3,175	0
Proceeds from exercise of stock options	5	0
Net cash provided by (used in) financing activities	37,287	-51
Net increase in cash and cash equivalents	33,920	261
Cash and cash equivalents at beginning of period	5,128	5,830
Cash and cash equivalents at end of period	$39,048	$6,091

Organization

Organization	9 Months Ended
	Sep. 30, 2014
Accounting Policies [Abstract]	'
Organization	'
	1. ORGANIZATION
	CareDx, Inc., (“CareDx” or the “Company”) is a commercial stage company that develops, markets and delivers a diagnostic surveillance solution for heart transplant recipients to help clinicians make personalized treatment decisions throughout a transplant patient’s lifetime. The Company’s commercialized testing solution, the AlloMap heart transplant molecular test (“AlloMap”), an FDA-cleared test, is a blood-based test used to monitor for acute cellular rejection in heart transplant recipients. The Company was incorporated in Delaware in December 1998, as Hippocratic Engineering, Inc. In April 1999, the Company changed its name to BioCardia, Inc., in June 2002 to Expression Diagnostics, Inc., in July 2007 to XDx, Inc. and in March 2014 to CareDx, Inc. The Company’s operations are based in Brisbane, California and it operates in one segment.
	Initial Public Offering
	On July 22, 2014, the Company closed its initial public offering (“IPO”) of 4,000,000 shares of its common stock, and issued an additional 220,000 shares of common stock on August 13, 2014 pursuant to the exercise of the over-allotment option granted to its underwriters. The public offering price of the shares sold in the offering was $10.00 per share. The total proceeds from the offering to the Company, net of underwriting discounts and commissions of $3.0 million, were $39.2 million. After deducting offering expenses payable by the Company of $3.8 million, net proceeds to the Company were $35.5 million. Upon the closing of the IPO, all shares of convertible preferred stock then outstanding converted into 6,048,220 shares of common stock, and a subordinated convertible note previously issued by the Company in the principal amount of $5.0 million converted into 510,777 shares of common stock. In addition, all of our convertible preferred stock warrants were converted into warrants to purchase common stock.
	Reverse Stock Split, and Increase in Authorized Shares
	On July 1, 2014, the Company’s Board of Directors approved an amendment to the Company’s Certificate of Incorporation to reflect a 1 for 6.85 reverse stock split (the “Reverse Stock Split”) of the Company’s outstanding common stock and convertible preferred stock and increase the authorized common stock to 10,000,000 shares, after giving effect to the Reverse Stock Split. The Reverse Stock Split became effective July 14, 2014. The par value per share was not adjusted as a result of the Reverse Stock Split. Effective July 22, 2014, the Company’s certificate of incorporation was amended and restated to provide for 100,000,000 authorized shares of common stock with a par value of $0.001 per share, and 10,000,000 authorized shares of preferred stock with a par value of $0.001 per share. All authorized, issued and outstanding shares of common stock, convertible preferred stock, options and warrants to purchase common or preferred stock and related per share amounts contained in the financial statements have been retroactively adjusted to reflect the Reverse Stock Split for all periods presented.

Summary_of_Significant_Account

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2014
Accounting Policies [Abstract]	'
Summary of Significant Accounting Policies	'
	2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
	Basis of Presentation
	The accompanying unaudited consolidated condensed financial statements include the accounts of CareDx, Inc. and its wholly-owned subsidiary, ImmuMetrix, Inc. All significant intercompany accounts and transactions have been eliminated in consolidation. In September 2014, the Company’s wholly-owned subsidiary, ImmuMetrix, Inc., was merged into CareDx, Inc., and as a result, at September 30, 2014, the financial statements of the former ImmuMetrix, Inc. are included in the financial statements of CareDx, Inc.
	The accompanying unaudited consolidated condensed financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”), and follow the requirements of the Securities and Exchange Commission (“SEC”) for interim reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by U.S. GAAP can be condensed or omitted. These financial statements have been prepared on the same basis as the Company’s annual financial statements and, in the opinion of management, reflect all adjustments, consisting only of normal recurring adjustments that are necessary for a fair statement of the Company’s financial information. The consolidated condensed balance sheet as of December 31, 2013 has been derived from audited financial statements as of that date but does not include all of the financial information required by U.S. GAAP for complete financial statements. Operating results for the three and nine months ended September 30, 2014 are not necessarily indicative of the results that may be expected for the year ending December 31, 2014.
	The accompanying consolidated condensed financial statements and related financial information should be read in conjunction with the audited financial statements and the related notes thereto for the year ended December 31, 2013 included in the Company’s Prospectus filed pursuant to Rule 424(b)(4) on July 18, 2014 with the SEC (the “Prospectus”).
	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 and the reported amounts of revenues and expenses in the financial statements and accompanying notes. On an ongoing basis, management evaluates its estimates, including those related to (i) revenue recognition, (ii) the differences between amounts billed and estimated receipts from payers, (iii) the determination of the accruals for clinical studies, (iv) the determination of refunds to be requested by third-party payers, (v) the fair value of assets and liabilities, (vi) the valuation of warrants to purchase convertible preferred stock, (vii) the determination of fair value of the Company’s common stock, (viii) the contingent consideration in a business acquisition, (ix) the fair value of the embedded derivative associated with the subordinated convertible note, (x) the determination of the valuation allowance and estimated tax benefit associated with deferred tax assets and net deferred tax liability, (xi) any impairment of long-lived assets including in-process technology and goodwill and (xii) legal contingencies. Actual results could differ from those estimates.
	Concentration of Credit Risk
	The Company is subject to credit risk from its accounts receivable which are derived from revenue earned from AlloMap tests provided for patients located in the U.S. and billed to various third-party payers. For the three months ended September 30, 2014 and 2013, 52% and 59%, respectively, of total revenue was derived from Medicare. For the nine months ended September 30, 2014 and 2013, 50% and 55%, respectively, of total revenue was derived from Medicare. No other payer represented more than 10% of testing revenue for these periods. At September 30, 2014, 63% of accounts receivable were from Medicare. No other payer represented more than 10% of accounts receivable at September 30, 2014.
	Fair Value of Financial Instruments
	Fair value is defined as the price that would be received from selling an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. When determining fair value, the Company considers the principal or most advantageous market in which the Company would transact, and it takes into consideration the assumptions that market participants would use when pricing the asset or liability. The Company’s assessment of the significance of a particular input to the fair value measurement of an asset or liability requires management to make judgments and to consider specific characteristics of that asset or liability.
	The carrying amounts of certain of the Company’s financial instruments, including cash equivalents, accounts receivable, accounts payable, and accrued liabilities, approximate fair value due to their short maturities. The carrying amount of the convertible preferred stock warrant liability and the subordinated convertible note equity call option liability (see Note 9) also represent their fair value.
	Cash Equivalents
	The Company considers all highly liquid investments that are readily convertible into cash having maturities at the time of purchase of three months or less to be cash equivalents. Cash equivalents include money market funds, obligations of U.S. government agencies, and government-sponsored entities which are carried at fair value.
	Testing Revenue
	The Company recognizes revenues for tests delivered when the following criteria are met: (i) persuasive evidence that an arrangement exists; (ii) delivery has occurred or services rendered; (iii) the fee is fixed or determinable; and (iv) collectability is reasonably assured.
	The first criterion is satisfied when a third-party payer makes a coverage decision or enters into a contractual arrangement with the Company for the test. The second criterion is satisfied when the Company performs the test and delivers the test result to the ordering physician. The third criterion is satisfied if the third-party payer’s coverage decision or reimbursement contract specifies a price for the test. The fourth criterion is satisfied based on management’s judgments regarding the collectability of the fees charged under the arrangement. Such judgments include review of past payment history. AlloMap testing may be considered investigational by some payers and not covered under their reimbursement policies. Others may cover the test, but not pay a set or determinable amount. As a result, in the absence of a reimbursement agreement or sufficient payment history, collectability cannot reasonably be assured so revenue is not recognized at the time the test is delivered.
	If all criteria set forth above are met, revenue is recognized. When the first, third or fourth criteria are not met but third-party payers make a payment to the Company for tests performed, the Company recognizes revenue on the cash basis in the period in which the payment is received.
	Revenue is recognized on the accrual basis net of adjustments for differences between amounts billed and the estimated receipts from payers. The amount the Company expects to collect may be lower than the agreed upon amount due to several factors, such as the amount of patient co-payments, the existence of secondary payers and claim denials. Estimated receipts are based upon historical payment practices of payers. Differences between estimated and actual cash receipts are recorded as an adjustment to revenue, which have been immaterial to date.
	Collaboration and License Revenue
	The Company generates revenue from collaboration and license agreements. Collaboration and license agreements may include non-refundable upfront payments, partial or complete reimbursement of research and development costs, contingent payments based on the occurrence of specified events under the agreements, license fees and royalties on sales of products or product candidates if they are successfully commercialized. The Company’s performance obligations under the collaborations may include the transfer of intellectual property rights in the form of licenses, obligations to provide research and development services and obligations to participate on certain development committees with the collaboration partners. The Company makes judgments that affect the periods over which it recognizes revenue. The Company periodically reviews its estimated periods of performance based on the progress under each arrangement and accounts for the impact of any change in estimated periods of performance on a prospective basis.
	The Company recognizes contingent consideration received from the achievement of a substantive milestone in its entirety in the period in which the milestone is achieved, which the Company believes is more consistent with the substance of its performance under its various license and collaboration agreements. The Company did not recognize any milestones during the three months or nine month periods ended September 30, 2014 or 2013.
	Cost of Testing
	Cost of testing reflects the aggregate costs incurred in delivering the Company’s AlloMap test results to clinicians. The components of cost of testing are materials and service costs, direct labor costs, including stock-based compensation, equipment and infrastructure expenses associated with testing samples, shipping, logistics and specimen processing charges to collect and transport samples and allocated overhead including rent, information technology, equipment depreciation and utilities and royalties. Costs associated with performing tests (except royalties) are recorded as the test is processed regardless of whether and when revenue is recognized with respect to that test. As a result, our cost of testing as a percentage of revenue may vary significantly from period to period because we do not recognize all revenue in the period in which the associated costs are incurred. Royalties for licensed technology, calculated as a percentage of test revenues, are recorded as license fees in cost of testing at the time the test revenues are recognized.
	Business Combinations
	In accordance with ASC 805, Business Combinations, the Company determines and allocates the purchase price of an acquired business to the tangible and identifiable intangible assets acquired and liabilities assumed based on their estimated fair values as of the business combination date, including identifiable intangible assets which either arise from a contractual or legal right or are separable from goodwill. The Company bases the estimated fair value of identifiable intangible assets acquired in a business combination on independent valuations that use information and assumptions provided by management, which consider management’s best estimates of inputs and assumptions that a market participant would use. The Company allocates any excess purchase price over the estimated fair value assigned to the net tangible and identifiable intangible assets acquired and liabilities assumed to goodwill. The use of alternative valuation assumptions, including estimated revenue projections, growth rates, royalty rates, cash flows, discount rates, estimated useful lives and probabilities surrounding the achievement of contingent milestones could result in different purchase price allocations and amortization expense in current and future periods.
	Goodwill and indefinite-lived intangible assets including acquired in-process technology are reviewed for impairment on an annual basis or more frequently if events or circumstances indicate that goodwill or indefinite-lived intangible assets may be impaired. The Company’s goodwill evaluation is based on both qualitative and quantitative assessments regarding the fair value of goodwill relative to its carrying value. The Company assesses qualitative factors to determine if its sole reporting unit’s fair value is more likely than not to exceed its carrying value, including goodwill. In the event the Company determines that it is more likely than not that its reporting unit’s fair value is less than its carrying amount, quantitative testing is performed comparing recorded values to estimated fair values. If the fair value exceeds the carrying value, goodwill is not impaired. If the carrying value exceeds the fair value, then the Company would calculate the potential impairment loss by comparing the implied fair value of goodwill with the carrying value. If the implied fair value of goodwill is less than the carrying value, then an impairment charge would be recorded. The Company performs its annual evaluation of goodwill during the fourth quarter of each fiscal year. Impairment losses on indefinite-lived intangible assets are recognized based solely on a comparison of the fair value of the asset to its carrying value, without consideration of any recoverability test.
	In those circumstances where an acquisition involves a contingent consideration arrangement that meets the definition of a liability under ASC 480, Distinguishing Liabilities from Equity, the Company recognizes a liability equal to the fair value of the contingent payments the Company expects to make as of the acquisition date. The Company remeasures this liability each reporting period and records changes in the fair value as a component of operating expenses.
	Transaction costs associated with these acquisitions are expensed as incurred in general and administrative expenses. Results of operations and cash flows of acquired companies are included in the Company’s operating results from the date of acquisition.
	Stock–Based Compensation
	The Company uses the Black-Scholes valuation model, which requires the use of estimates such as stock price volatility and expected option lives, to value employee stock options. The Company estimates the expected option lives using historical data, volatility using data of similar companies in the diagnostics industry, and risk-free rates based on the implied yield currently available in the U.S. Treasury zero-coupon issues with a remaining term equal to the expected option lives, and dividend yield based on the Company’s historical data.
	The Company uses the straight-line attribution method for recognizing compensation expense. Compensation expense is recognized on awards ultimately expected to vest and reduced for forfeitures that are estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates. Forfeitures are estimated based on the Company’s historical experience.
	Equity instruments granted to nonemployees are valued using the Black-Scholes valuation model and are subject to periodic revaluation over their vesting terms. Nonemployee stock compensation is recognized upon vesting of the stock options which is commensurate with the period over which services are provided.
	Impairment
	The Company evaluates its long-lived assets for indicators of possible impairment when events or changes in circumstances indicate the carrying amount of an asset may not be recoverable. The Company then compares the carrying amounts of the assets with the future net undiscounted cash flows expected to be generated by such asset. Should an impairment exist, the impairment loss would be measured based on the excess carrying value of the asset over the asset’s fair value determined using discounted estimates of future cash flows. The Company has not identified any such impairment losses to date.
	Warrants
	At September 30, 2014, the Company had freestanding warrants enabling counterparties to purchase shares of its common stock. Prior to the Company’s initial public offering in July 2014, the Company also had freestanding warrants enabling counterparties to purchase shares of its convertible preferred stock. In accordance with the accounting guidance regarding distinguishing liabilities from equity, freestanding warrants for convertible preferred stock that are contingently redeemable are classified as liabilities on the balance sheets and are recorded at their estimated fair value. These warrants are remeasured at each balance sheet date, and any change in estimated fair value is recognized in other income (expense), net on the statements of operations. Prior to the IPO, the Company adjusted the liability for changes in estimated fair value until the earlier of the exercise or expiration of the warrants. Upon the IPO, certain preferred stock warrants were converted into warrants to purchase common stock, and, accordingly, the liability was reclassified to equity, while other warrants expired pursuant to their terms.
	The Company accounts for its warrants to purchase shares of common stock as equity in accordance with the accounting guidance distinguishing liabilities from equity.
	Comprehensive Income (Loss)
	Net income (loss) and comprehensive income (loss) are the same for all periods presented.
	Recent Accounting Pronouncements
	In May 2014, the Financial Accounting Standards Board issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606) (“ASU 2014-09”), which amends the existing accounting standards for revenue recognition. ASU 2014-09 is based on principles that govern the recognition of revenue at an amount an entity expects to be entitled to when products are transferred to customers. ASU 2014-09 will be effective for the Company beginning in its first quarter of 2017. Early adoption is not permitted. The new revenue standard may be applied retrospectively to each prior period presented or retrospectively with the cumulative effect recognized as of the date of adoption. The Company is currently evaluating the impact of adopting the new revenue standard on its financial statements.

Net_Income_Loss_Per_Share

Net Income (Loss) Per Share	9 Months Ended
	Sep. 30, 2014
Earnings Per Share [Abstract]	'
Net Income (Loss) Per Share	'
	3. NET INCOME (LOSS) PER SHARE
	Basic net income (loss) per share has been computed by dividing the net income (loss) by the weighted-average number of common shares outstanding during the period, without consideration for common share equivalents.
	Diluted net income (loss) per share has been computed by dividing the net income (loss) by the sum of the weighted-average number of common shares and common share equivalents outstanding during the period, to the extent that such common share equivalents are dilutive.
	For the three and nine months ended September 30, 2014, certain common share equivalents have been included in diluted net income per share, as their effect is dilutive. For the three and nine months ended September 30, 2014, common share equivalents include: (i) options and warrants to purchase common stock; (ii) options and warrants to purchase convertible preferred stock prior to their conversion into options and warrants to purchase common stock upon the IPO on July 22, 2014; and (iii) convertible preferred stock and the subordinated convertible note prior to their conversion into common stock upon the IPO. Common share equivalents for convertible preferred stock and the subordinated convertible note are determined using the if-converted method. Common share equivalents for options and warrants are determined using the treasury-stock method.
	For the three and nine months ended September 30, 2013, all common share equivalents have been excluded from the calculation of diluted net loss per share, as the effect would be antidilutive.
	The following tables set forth the computation of the Company’s basic and diluted net income (loss) per share (in thousands, except shares and per share data):
		Three Months Ended						Nine Months Ended
		September 30,						September 30,
		2014			2013			2014			2013
	Numerator:
	Net income (loss)	$	1,213		$	(830	)	$	786		$	(2,980	)
	Add: interest expense related to subordinated convertible note		231			—			364			—
	Less: gain on change in fair value of derivative related to subordinated convertible note		—			—			(118	)		—
	Less: gain on extinguishment of derivative related to subordinated convertible note		(120	)		—			(120	)		—
	Net income (loss) attributable to common stockholders	$	1,324		$	(830	)	$	912		$	(2,980	)
	Denominator:
	Weighted-average shares used to compute basic net income (loss) per share attributable to common stockholders		9,279,649			1,011,136			3,798,559			1,011,001
	Effect of potentially dilutive securities:
	Shares of common stock subject to conversion from preferred stock		1,446,313			—			3,973,622			—
	Shares of common stock subject to conversion from subordinated convertible note		122,142			—			179,614			—
	Shares of common stock subject to outstanding options		371,273			—			347,108			—
	Weighted-average shares used to compute diluted net income (loss) per share attributable to common stockholders		11,219,377			1,011,136			8,298,903			1,011,001
	Net income (loss) per share attributable to common stockholders:
	Basic	$	0.13		($	0.82	)	$	0.21		($	2.95	)
	Diluted	$	0.12		($	0.82	)	$	0.11		($	2.95	)
	The following potentially dilutive securities have been excluded from diluted net income (loss) per share, because their effect would be antidilutive:
		Three Months Ended						Nine Months Ended
		September 30,						September 30,
		2014			2013			2014			2013
	Shares of common stock subject to conversion from preferred stock		—			5,160,085			—			5,160,085
	Shares of common stock subject to outstanding options		514,370			491,259			514,370			491,259
	Shares of common stock subject to outstanding warrants		266,586			623,803			266,586			623,803
	Total		780,956			6,275,147			780,956			6,275,147
	Shares contingently issuable upon the achievement of a future milestone in conjunction with the Company’s business combination with ImmuMetrix, Inc. (see Note 11) are not included in the above table due to the uncertainty of the Company achieving this performance metric.

Fair_Value_Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2014
Fair Value Disclosures [Abstract]	'
Fair Value Measurements	'
	4. FAIR VALUE MEASUREMENTS
	The Company’s financial instruments are measured and recorded at fair value except for debt, which is recorded at amortized cost. The accounting guidance establishes a three-tiered hierarchy, which prioritizes the inputs used in the valuation methodologies in measuring fair value as follows:
		•		Level 1: Inputs which include quoted prices in active markets for identical assets and liabilities.
		•		Level 2: Inputs other than Level I that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.
		•		Level 3: Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.
	The following table sets forth the fair value of the Company’s financial assets and liabilities measured on a recurring basis, as of September 30, 2014 and December 31, 2013 (in thousands):
			September 30, 2014
			Level 1			Level 2			Level 3			Total
	Assets
	Money market funds		$	38,964		$	—		$	—		$	38,964
	Liabilities
	Contingent consideration		$	—		$	—		$	1,037		$	1,037
	Total liabilities		$	—		$	—		$	1,037		$	1,037
			December 31, 2013
			Level 1			Level 2			Level 3			Total
	Assets
	Money market funds		$	5,204		$	—		$	—		$	5,204
	Liabilities
	Warrants to purchase convertible preferred stock		$	—		$	—		$	525		$	525
	Total liabilities		$	—		$	—		$	525		$	525
	The Company recognizes transfers between levels of the fair value hierarchy as of the end of the reporting period. There were no transfers between Level 1, Level 2 and Level 3 categories during the periods presented.
	In determining fair value, the Company uses various valuation approaches within the fair value measurement framework. The valuation methodologies used for the Company’s instruments measured at fair value and their classification in the valuation hierarchy are summarized below:
		•		Money market funds - Investments in money market funds are classified within Level 1. At September 30, 2014 and December 31, 2013, money market funds were included on the balance sheets in cash and cash equivalents and in restricted cash.
		•		Contingent consideration - As of September 30, 2014, the Company had a contingent obligation to issue 227,845 shares of the Company’s common stock to the former owners of ImmuMetrix, Inc. in conjunction with the Company’s acquisition of ImmuMetrix, Inc. (see Note 11). The issuance will occur if the Company completes 2,500 commercial tests involving the measurement of cfDNA in organ transplant recipients in the United States by June 10, 2020. The Company recorded its estimate of the fair value of the contingent consideration based on its evaluation of the probability of the achievement of the contractual conditions that would result in the payment of the contingent consideration. The fair value of the contingent consideration was estimated using the fair value of the shares to be paid if the contingency is met multiplied by management’s 65% estimate at September 30, 2014 of the probability of success. The significant input in the Level 3 measurement not supported by market activity is the Company’s probability assessment of the milestone being met. The value of the liability is subsequently remeasured to fair value each reporting date, and the change in estimated fair value is recorded to a component of operating expenses until the milestone contingency is paid, expires or is no longer achievable. Increases (decreases) in the estimation of the probability percentage result in a directionally similar impact to the fair value measurement of the contingent consideration liability.
		•		Derivative liability related to subordinated convertible note – On April 17, 2014, the Company issued a $5.0 million subordinated convertible promissory note to Illumina, Inc. that had some features that constituted embedded derivatives. The Company determined that the optional conversion or repayment upon a change in control is an equity call option with a potentially variable value to be received and meets the definition of a derivative which would be required to be bifurcated. The estimated fair value of this embedded derivative was affected by the estimated probability assigned to the various scenarios for the host instrument. As of April 17, 2014, management estimated repayment upon a change in control within the loan term at a 10% probability. As of June 30, 2014 management estimated repayment upon a change in control within the loan term at a 5% probability. The $239,000 original estimated fair value of the embedded derivative liability was included in accrued and other liabilities. At June 30, 2014, the fair value of the derivative was remeasured to $120,000, resulting in a gain of $119,000, which was recorded in other income in the statements of operations for the three months ended June 30, 2014. Upon the Company’s IPO in July 2014, the fair value of the derivative became $0, and a gain of $120,000 was recorded in other income. The significant unobservable input used in the fair value measurement of the derivative liability was the probability assigned to the various scenarios. Generally, increases (decreases) in the probability of the factors primarily impacting the valuation would result in a directionally similar impact to the fair value measurement of the derivative liability. Changes in estimated fair value were recognized in other income (expense) on the statements of operations.
		•		Warrants to purchase convertible preferred stock – At December 31, 2013, the Company’s warrants to purchase convertible preferred stock were classified as Level 3 because they were valued based on unobservable inputs and management’s judgment due to the absence of quoted market prices, inherent lack of liquidity and the long-term nature of such financial instruments. These assumptions are inherently subjective and involve significant management judgment. The significant unobservable input used in the fair value measurement of the warrant liability was the fair value of the underlying convertible preferred stock at the valuation remeasurement date. Generally, increases (decreases) in the fair value of the underlying stock would result in a directionally similar impact to the fair value measurement of the preferred stock warrants. Any change in estimated fair value is recognized in other income or expense on the statements of operations. Upon the Company’s IPO in July 2014, certain warrants to purchase convertible preferred stock were converted into warrants to purchase common stock and were reclassified to equity, while other warrants to purchase preferred stock expired pursuant to their terms.
	The Company’s liabilities classified as Level 3 were valued based on unobservable inputs and management’s judgment due to the absence of quoted market prices, inherent lack of liquidity and the long-term nature of the financial instruments.
	The estimated fair value of the convertible preferred stock warrant liability as of December 31, 2013 was determined using the Black-Scholes option pricing model using the following assumptions:
	Estimated fair value of common stock		$	12.4
	Risk-free interest rate			0.8% - 2.1%
	Volatility			40% - 45%
	Estimated term equal to the remaining contractual term			3.3 - 5.6 years
	Expected dividend yield			—
	The following table presents the issuances, changes in fair value and reclassifications of the Company’s Level 3 financial instruments that are measured at fair value on a recurring basis (in thousands):
			Level 3
			Contingent			Warrants			Derivative			Total
			Consideration			to Purchase			Liability
			Liability			Convertible			Related to
						Preferred			Subordinated
						Stock			Convertible
									Note
	Balance as of December 31, 2013		$	—		$	525		$	—		$	525
	Issuance of financial instruments			2,313			—			239			2,552
	Change in estimated fair value			(1,276	)		14			(239	)		(1,501	)
	Reclassification to stockholders’ equity			—			(539	)		—			(539	)
	Balance as of September 30, 2014		$	1,037		$	—		$	—		$	1,037

Inventory

Inventory	9 Months Ended
	Sep. 30, 2014
Inventory Disclosure [Abstract]	'
Inventory	'
	5. INVENTORY
	The following table summarizes the Company’s inventory (in thousands):
		September 30,		December 31,
		2014		2013
	Finished goods	$	234	$	230
	Raw materials		262		288
	Total inventory	$	496	$	518

Accrued_and_Other_Liabilities

Accrued and Other Liabilities	9 Months Ended
	Sep. 30, 2014
Payables and Accruals [Abstract]	'
Accrued and Other Liabilities	'
	6. ACCRUED AND OTHER LIABILITIES
	The following table represents the components of accrued and other liabilities (in thousands):
		September 30,		December 31,
		2014		2013
	Accrued professional fees	$	391	$	175
	Accrued test sample processing fees		260		195
	Consideration payable in connection with business combination		194		—
	Deferred rent – current portion		187		145
	Accrued clinical studies		135		84
	Accrued overpayments and refunds		98		215
	Accrued interest		98		—
	Capital leases – current portion		79		43
	Other accrued expenses		469		191
		$	1,911	$	1,048

Commitments_and_Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2014
Commitments and Contingencies Disclosure [Abstract]	'
Commitments and Contingencies	'
	7. COMMITMENTS AND CONTINGENCIES
	Royalty Commitments
	In November 2004, the Company entered into a license agreement with Roche Molecular Systems, Inc., or Roche, that grants the Company the right to use certain Roche technology relating to polymerase chain reaction, or PCR, and quantitative real-time PCR, in clinical laboratory services, including in connection with AlloMap. This is a non-exclusive license agreement in the United States covering claims in multiple Roche patents. The Company had disputed the combination services percentage Roche sought to apply under the agreement. The combination service percentage is a multiplier used to calculate royalties where licensed services are sold in combination with other services. From July 2011 through September 2014, the Company withheld payment of such royalties pending resolution of the matter. On February 11, 2014, Roche filed a demand for arbitration with the American Arbitration Association seeking a declaration that the Company had materially breached the Roche license agreement by failing to report and pay royalties owing to Roche in respect of licensed services performed by the Company after July 1, 2011. Since July 1, 2011, the Company fully accrued the unpaid royalties on the balance sheets, and the amount of the unpaid royalties has been reflected as an expense in the Company’s income statements in the periods to which the royalties relate.
	On September 11, 2014, the Company entered into a settlement and mutual release agreement with Roche whereby: (i) for the period beginning July 1, 2011 through June 30, 2014, the Company agreed to pay the amount of $2,827,220 in settlement of past royalties due; (ii) for the period beginning July 1, 2014 through September 30, 2014, the Company agreed to pay royalties based on the same combination services percentage used to determine the past royalties due; (iii) for the period beginning October 1, 2014 through September 30, 2017, Roche and the Company agreed to a downward adjustment of the combination services percentage used to determine the portion of the AlloMap testing revenue that is royalty bearing under the terms of the license; (iv) the Company agreed to report and pay quarterly royalties within 45 days of the end of each calendar quarter; (v) Roche agreed that, subject to the Company’s timely payment of all applicable royalties through such date, no further royalties will be payable by the Company for periods after September 30, 2017; (vi) the Company and Roche agreed to mutually release all claims under the license agreement through the settlement date; and (vii) Roche agreed to dismiss the arbitration claims. For all time periods, the contractual royalty rate in the license agreement was or will be applied to the applicable combination services percentage to determine the royalties payable for the AlloMap service.
	Under the license agreement, the Company incurs royalty expenses as a percentage of combination services revenue and classifies those expenses as a component of cost of testing in the statements of operations. As a result of the Company’s September 2014 settlement and payment to Roche of $2.8 million as payment in full of all royalties under the license agreement from July 1, 2011 through June 30, 2014, the Company recorded a reduction of $566,000 to cost of testing and $132,000 to interest expense in the statements of operations for the three and nine months ended September 30, 2014. Of the $2.8 million paid by the Company under the terms of the settlement agreement, $0.4 million represented royalties on AlloMap revenue for the six months ended December 31, 2011, $0.9 million represented royalties on AlloMap revenue for the year ended December 31, 2012, $1.0 million represented royalties on AlloMap revenue for the year ended December 31, 2013, and $0.5 million represented royalties on AlloMap revenue for the nine months ended September 30, 2014.

Collaboration_and_Licensing_Ag

Collaboration and Licensing Agreements	9 Months Ended
	Sep. 30, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
Collaboration and Licensing Agreements	'
	8. COLLABORATION AND LICENSING AGREEMENTS
	Laboratory Corporation of America Holdings (“LabCorp”)
	In April 2012, CareDx and LabCorp entered into a collaboration and license agreement (“2012 Agreement”) to develop a lupus flare predictor test. The agreement provided for CareDx to license technology to LabCorp. Of the total arrangement consideration, the fair value of the license was assessed to be $1.0 million. The license term in the 2012 Agreement was the later of 10 years from the date of the agreement or the expiration of the last-to-expire patents and patent applications included in the CareDx technology licensed to LabCorp, unless the license were terminated by mutual agreement. The agreement provided that CareDx and LabCorp would share equally the costs of developing the lupus flare predictor test; however LabCorp’s share of the development cost was subject to certain limits at each stage of the arrangement.
	Under the agreement, in 2012 LabCorp paid the Company a nonrefundable and non-creditable upfront license fee payment of $1,000,000, and a nonrefundable and non-creditable payment of $250,000 for certain lupus samples. The Company was to receive royalties in the high single digits from LabCorp on net sales of the commercialized flare predictor test or other tests developed using the samples sold.
	Phase 1 of the project was completed in the first quarter of 2014.
	On September 18, 2014, CareDx and LabCorp terminated the 2012 agreement. The termination agreement provides that:
		•	CareDx transfer and assign to LabCorp, 300 “SAGE I” clinical samples and related clinical data and documentation that CareDx obtained from patients during the discovery phase of the collaboration;
		•	CareDx grant a perpetual, non-exclusive worldwide, fully paid, sublicensable, royalty-free license to use any collaboration intellectual property and data for any and all purposes; and
		•	LabCorp pay $500,000 to CareDx within 30 days of CareDx’s delivery of the clinical samples and clinical data and documentation. No further royalties, milestone fees or other fees will be payable by LabCorp after the termination date.
	As of September 30, 2014, $611,000 of the upfront license fee was included in current deferred revenue. That amount, plus the $500,000 termination fee, will be recognized as collaboration and license revenue upon CareDx’s delivery to LabCorp of the clinical samples and clinical data and documentation during the three months ending December 31, 2014.
	During the three months ended September 30, 2014 and 2013, the Company recognized $0 and $64,000, respectively, in revenue under this arrangement, which consisted of amortization of upfront license fee of $0 and $47,000, respectively, and reimbursement of research and development expenses of $0 and $17,000, respectively. During the nine months ended September 30, 2014 and 2013, the Company recognized $31,000 and $331,000, respectively, in revenue under this arrangement, which consisted of amortization of upfront license fee of $15,000 and $172,000, respectively, and reimbursement of research and development expenses of $16,000 and $159,000, respectively. Such revenues are included in collaboration and license revenue on the statements of operations.
	Included in research and development expenses were $0 and $34,000 for the three months ended September 30, 2014 and 2013, respectively, for development costs associated with the 2012 Agreement. Such amounts were $32,000 and $318,000 for the nine months ended September 30, 2014 and 2013, respectively.
	Diaxonhit (“DHT”)
	In June 2013, the Company entered into an exclusive Distribution and Licensing Agreement with DHT, a French public company, whereby DHT will have the AlloMap test performed in a European laboratory and commercialize the test in the European Economic Area (“EEA”). The agreement will expire at the later of the last-to-expire patent in the EEA or ten years from the first commercial sale of the test in the EEA, which is expected to occur in late 2014 or early 2015.
	Consideration under the agreement includes an upfront cash payment of approximately €387,500 ($503,000) that is designated to offset royalties earned by the Company in the first three years following the first commercial sale. The Company is entitled to receive royalties from DHT as a percent of net sales, as defined in the agreement, of AlloMap tests in the mid to high teens. Approximately €250,000 ($344,000) of the upfront payments is refundable under certain circumstances. Upon confirmation that the CE mark was in place, the Company also received an equity payment of DHT common stock with a value of €387,500 ($503,000). These shares were promptly sold by the Company in July 2013 for total consideration of $467,000.
	Other consideration that may be earned by the Company includes agreed-upon per unit pricing for the supply of AlloMap products, and additional royalties that are payable upon the achievement of various sales milestones by DHT. In this arrangement, there is one combined unit of accounting.
	Commercial sales have not yet begun in the EEA. However, the Company has delivered a small number of AlloMap-related services to DHT. Total revenue recognized from this arrangement through September 30, 2014 is immaterial.
	CardioDx, Inc. (“CDX”)
	In 2005, the Company entered into a services agreement with a related party, CDX, whereby the Company provided CDX with biological samples and related data and performed laboratory services on behalf of CDX. Each company granted the other a worldwide license under certain of its intellectual property rights. Pursuant to this agreement, CDX pays royalties to the Company of a low single-digit percentage of the cash collected from sales of CDX licensed products. In 2009, CDX terminated the services portion of this agreement, however, the royalty obligation from CDX continues until the tenth anniversary of the first commercial sale of a CDX licensed product. The first commercial sale of such product by CDX occurred in 2009, therefore the royalty obligation to the Company continues until 2019. One board member of CDX serves on the Company’s board of directors and is affiliated with stockholders of the Company. Royalty revenues, recorded when earned, were $49,000 and $27,000 for the three months ended September 30, 2014 and 2013, respectively. Such amounts were $167,000 and $57,000 for the nine months ended September 30, 2014 and 2013, respectively. The Company had receivable balances from CDX of $49,000 and $37,000 at September 30, 2014 and December 31, 2013, respectively.

Subordinated_Convertible_Note

Subordinated Convertible Note	9 Months Ended
	Sep. 30, 2014
Debt Disclosure [Abstract]	'
Subordinated Convertible Note	'
	9. SUBORDINATED CONVERTIBLE NOTE
	On April 17, 2014, the Company issued a $5.0 million Subordinated Convertible Promissory Note to Illumina, Inc. (the “Note”) which provides for interest at an annual rate of 8.0%. The Note matures one year following its issuance with principal and unpaid interest due at that time unless the Note is converted into equity prior to the maturity date. As described below, conversion is mandatory in the event of a Qualified Initial Public Offering (as defined in the Note). Upon the closing of the IPO on July 22, 2014, the Note converted into 510,777 shares of common stock in accordance with its terms.
	The original estimated fair value of the embedded derivative was accounted for as a debt discount to the subordinated convertible note payable on the consolidated condensed balance sheet. The estimated fair value of the embedded derivative liability was included in accrued and other liabilities on the condensed balance sheets. Amortization of the debt discount was $51,000 for the period from April 17, 2014 to June 30, 2014, and $205,000 for the period from July 1, 2014 until July 22, 2014, when the Note was converted into common stock. Extinguishment of the embedded derivative liability at July 22, 2014 resulted in other income of $120,000 for the three months ended September 30, 2014.

Stock_Option_Plans

Stock Option Plans	9 Months Ended
	Sep. 30, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Stock Option Plans	'
	10. STOCK OPTION PLANS
	Prior to its IPO, the Company had one active stock option plan, the 2008 Equity Incentive Plan, one assumed stock option plan, the ImmuMetrix 2013 Equity Incentive Plan, and one terminated stock option plan, the 1998 Stock Plan.
	Upon its IPO, the Company reserved 838,695 shares of common stock for issuance under a new 2014 Equity Incentive Plan (“2014 Plan”). The shares reserved for issuance under the 2014 Plan also include shares returned to the 2008 Plan as the result of expiration or termination of options, provided that the maximum number of shares that may be added to the 2014 Plan thereby is limited to a maximum of 865,252 shares. The number of shares available for issuance under the 2014 Plan will also include an annual increase on the first day of each year beginning in 2014, equal to the least of:
		•		357,075 shares
		•		4.0% of the outstanding shares of common stock as of the last day of the immediately preceding year; or
		•		such other number of shares as the Company’s board of directors may determine.
	The following table summarizes option activity and related information during the nine months ended September 30, 2014 under the 2014 Equity Incentive Plan, the ImmuMetrix 2013 Equity Incentive Plan and the 2008 Plan and for options that remain outstanding under such plans:
			Nine Months Ended
			30-Sep-14
						Options Outstanding
			Shares			Number of			Weighted-
			Available			Shares			average
			for Grant						Exercise
									Price
	Beginning balance			332,995			466,965		$	1.99
	Increase in shares reserved for issuance			940,884			—		$	—
	Granted			(530,570	)		530,570		$	12.1
	Assumed in business combination			—			23,229		$	2.06
	Exercised			—			(3,038	)	$	2.04
	Forfeited			18,983			(18,983	)	$	10.31
	Expired			12,638			(12,638	)	$	2.85
	Ending balance			774,930			986,105		$	7.41
	The weighted-average grant-date fair value of options granted during the nine months ended September 30, 2014 using the Black-Scholes valuation model was $5.07 per share.
	Options outstanding and exercisable that have vested or are expected to vest as of September 30, 2014 are as follows:
			Number			Weighted-			Weighted-			Aggregate
			of Shares			average			average			Intrinsic
						Exercise			Remaining			Value(in
						Price			Contractual			thousands)
									Life(Years)
	Vested			389,976		$	2.69			6.17		$	1,775
	Expected to vest			596,129		$	10.51			9.31		$	593
	Total			986,105		$	7.41			8.07		$	2,368
	In the table above, aggregate intrinsic value represents the difference between the exercise price and the $7.00 price per share of the Company’s common stock as of September 30, 2014.
	The Company’s results of operations include expense relating to employee and nonemployee stock-based payment awards as follows (in thousands):
			Three Months Ended						Nine Months Ended
			September 30,						September 30,
			2014			2013			2014			2013
	Cost of testing		$	6		$	1		$	15		$	3
	Research and development			35			2			57			6
	Sales and marketing			13			—			22			2
	General and administrative			111			16			256			46
			$	165		$	19		$	350		$	57
	Valuation Assumptions
	The fair value of stock-based awards was estimated using the Black-Scholes option-pricing model using the following weighted-average assumptions:
			Three Months Ended						Nine Months Ended
			September 30,						September 30,
			2014			2013			2014			2013
	Risk-free interest rate			2.05	%		1.72	%		1.76	%		1.09	%
	Volatility			43.81	%		45.03	%		42.3	%		45.37	%
	Expected term, in years			6			6			5.3			6
	Expected dividend yield			0	%		0	%		0	%		0	%
	At September 30, 2014, there was approximately $2.3 million of total unrecognized stock-based compensation, net of estimated forfeitures, related to nonvested employee stock option awards granted that will be recognized on a straight-line basis over the remaining vesting period of 3.1 years.

Business_Combination

Business Combination	9 Months Ended
	Sep. 30, 2014
Business Combinations [Abstract]	'
Business Combination	'
	11. BUSINESS COMBINATION
	On June 10, 2014, in accordance with an agreement and plan of merger, the Company acquired ImmuMetrix, Inc. (“IMX”), a privately held development stage company working in new technologies using cell-free donor DNA (“cfDNA”) technology for the diagnosis, treatment and management of transplant rejection, immune disorders and diseases, including the development of a new, non-invasive test designed to detect the early stages of solid organ transplant rejection. The Company acquired all IMX assets associated with transplant diagnostics, including related immune repertoire and infectious diseases. An IMX successor company retained the limited assets not associated with transplant diagnostics. The acquisition was structured as a tax-free reorganization.
	The Company acquired all of the issued and outstanding capital stock of IMX for the total estimated purchase price of $17.2 million consisting of $600,000 in cash; 911,364 shares of the Company’s Series G convertible preferred stock with an estimated fair value of $14.2 million, including 23,229 shares of the Company’s Series G convertible preferred stock with an estimated fair value of $369,000 as a result of the Company’s assumption of IMX outstanding stock options; and an additional payment of 227,845 shares of CareDx Series G convertible preferred stock if a future milestone is achieved. The Agreement provides that the milestone will be achieved if the Company completes 2,500 commercial tests involving the measurement of cfDNA in organ transplant recipients in the United States no later than six years after the closing date of the acquisition. All shares of Series G Preferred Stock and options to acquire Series G Preferred Stock converted into common stock and options to acquire common stock immediately prior to the closing of the Company’s initial public offering. The additional shares to be paid for the achievement of the milestone will also be issued in common stock. The fair value of this contingent consideration was $2.3 million at the acquisition date and at June 30, 2014, and $1.0 million at September 30, 2014.
	The intellectual property acquired includes an exclusive license from Stanford University to a patent relating to the diagnosis of rejection in organ transplant recipients using cfDNA. The license provides for the Company to pay royalties to Stanford University on sales of the Company’s cfDNA tests.
	IMX’s post-acquisition results of operations for the period from June 11, 2014 through September 30, 2014 are included in the Company’s consolidated condensed statements of operations.
	Pro Forma Impact of the Acquisition of IMX
	The following table presents pro forma results of operations and gives effect to the IMX transaction as if the transaction had been consummated on January 1, 2013. The unaudited pro forma results of operations have been prepared for comparative purposes only and are not necessarily indicative of what would have occurred had the business combination been completed at the beginning of the period or of the results that may occur in the future. Furthermore, the pro forma financial information does not reflect the impact of any reorganization or operating efficiencies resulting from combining the two companies (in thousands, except per share data).
		Nine Months Ended
		September 30,
		2014			2013
	Net revenue	$	19,354		$	16,243
	Net income (loss)	$	(1,075	)	$	(2,904	)
	Net income (loss) per common share - basic	$	(0.28	)	$	(2.87	)
	Net income (loss) per common share - diluted	$	(0.28	)	$	(2.87	)
	The unaudited pro forma consolidated financial information was prepared using the acquisition method of accounting and is based on the historical financial information of the Company and IMX, reflecting the Company’s and IMX’s results of operations for the nine month periods ended September 30, 2014 and 2013. The historical financial information has been adjusted to give effect to the pro forma events that are: (i) directly attributable to the acquisition, (ii) factually supportable and (iii) expected to have a continuing impact on the combined results. The unaudited pro forma consolidated financial information reflects: (a) the removal of acquisition-related costs of $1.7 million incurred by both CareDx and IMX for the nine months ended September 30, 2014 including the removal of $0.2 million of IMX stock-based compensation expense that resulted from modifications to options in anticipation of the acquisition; (b) the removal of a $1.5 million tax benefit for the nine months ended September 30, 2014 that resulted from the acquisition; (c) the addition of salaries, benefits and fees for IMX employees and consultants retained after the acquisition; and (d) the addition of the $1.5 million acquisition-related tax benefit for the nine months ended September 30, 2013, as if the acquisition had occurred on January 1, 2013 and the benefit had been recognized during the nine months ended September 30, 2013. Acquisition related expenses are primarily included in general and administrative expenses.

Debt

Debt	9 Months Ended
	Sep. 30, 2014
Transfers and Servicing [Abstract]	'
Debt	'
	12. DEBT
	In August 2012, the Company entered into a $15,000,000 loan and security agreement. In August 2013, the Company amended the loan to defer the beginning of principal repayment for six months, to March 1, 2014. To obtain this deferral, there was an additional fee of $150,000 due at the end of the loan term. The loan, as amended, provides for interest-only payments for 18 months through February 28, 2014 followed by 30 equal monthly principal and interest payments of $566,822 at an annual interest rate of 9.95%. In addition, a final payment of $1,275,000 will be due at the end of the loan term. The loan also included a facility fee of $75,000.
	In connection with the loan, the Company issued to the lenders warrants to purchase 167,181 shares of Series G convertible preferred stock at $21.78 per share. The warrants are exercisable until 2019. Upon the Company’s IPO on July 22, 2014, the warrants became warrants to purchase common stock.
	The loan is collateralized by a security interest in all of the Company’s assets except intellectual property on which there is a negative pledge, and the loan agreement contains covenants, including a revenue covenant, and restrictions on the Company’s ability to pay cash dividends. At September 30, 2014 and December 31, 2013, the Company was in compliance with all loan covenants.

Income_Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2014
Income Tax Disclosure [Abstract]	'
Income Taxes	'
	13. INCOME TAXES
	In connection with the Company’s June 2014 acquisition of ImmuMetrix, Inc., a tax benefit of $1.5 million was recognized during the nine months ended September 30, 2014. This benefit resulted from the expectation that amortization of the in-process technology acquired, when completed and placed in service, is not expected to be deductible for tax purposes, as the transaction was structured as a tax-free reorganization. Accordingly, a deferred tax liability was recorded at the acquisition date for the difference between the financial reporting and tax basis of the acquired in-process technology. While the in-process technology is considered an indefinite lived intangible asset, this asset is expected to be amortized or impaired prior to the expiration of net operating loss carryforwards available to the Company.

Organization_Policies

Organization (Policies)	9 Months Ended
	Sep. 30, 2014
Accounting Policies [Abstract]	'
Reverse Stock Split, and Increase in Authorized Shares	'
	Reverse Stock Split, and Increase in Authorized Shares
	On July 1, 2014, the Company’s Board of Directors approved an amendment to the Company’s Certificate of Incorporation to reflect a 1 for 6.85 reverse stock split (the “Reverse Stock Split”) of the Company’s outstanding common stock and convertible preferred stock and increase the authorized common stock to 10,000,000 shares, after giving effect to the Reverse Stock Split. The Reverse Stock Split became effective July 14, 2014. The par value per share was not adjusted as a result of the Reverse Stock Split. Effective July 22, 2014, the Company’s certificate of incorporation was amended and restated to provide for 100,000,000 authorized shares of common stock with a par value of $0.001 per share, and 10,000,000 authorized shares of preferred stock with a par value of $0.001 per share. All authorized, issued and outstanding shares of common stock, convertible preferred stock, options and warrants to purchase common or preferred stock and related per share amounts contained in the financial statements have been retroactively adjusted to reflect the Reverse Stock Split for all periods presented.
Basis of Presentation	'
	Basis of Presentation
	The accompanying unaudited consolidated condensed financial statements include the accounts of CareDx, Inc. and its wholly-owned subsidiary, ImmuMetrix, Inc. All significant intercompany accounts and transactions have been eliminated in consolidation. In September 2014, the Company’s wholly-owned subsidiary, ImmuMetrix, Inc., was merged into CareDx, Inc., and as a result, at September 30, 2014, the financial statements of the former ImmuMetrix, Inc. are included in the financial statements of CareDx, Inc.
	The accompanying unaudited consolidated condensed financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”), and follow the requirements of the Securities and Exchange Commission (“SEC”) for interim reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by U.S. GAAP can be condensed or omitted. These financial statements have been prepared on the same basis as the Company’s annual financial statements and, in the opinion of management, reflect all adjustments, consisting only of normal recurring adjustments that are necessary for a fair statement of the Company’s financial information. The consolidated condensed balance sheet as of December 31, 2013 has been derived from audited financial statements as of that date but does not include all of the financial information required by U.S. GAAP for complete financial statements. Operating results for the three and nine months ended September 30, 2014 are not necessarily indicative of the results that may be expected for the year ending December 31, 2014.
	The accompanying consolidated condensed financial statements and related financial information should be read in conjunction with the audited financial statements and the related notes thereto for the year ended December 31, 2013 included in the Company’s Prospectus filed pursuant to Rule 424(b)(4) on July 18, 2014 with the SEC (the “Prospectus”).
Use of Estimates	'
	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 and the reported amounts of revenues and expenses in the financial statements and accompanying notes. On an ongoing basis, management evaluates its estimates, including those related to (i) revenue recognition, (ii) the differences between amounts billed and estimated receipts from payers, (iii) the determination of the accruals for clinical studies, (iv) the determination of refunds to be requested by third-party payers, (v) the fair value of assets and liabilities, (vi) the valuation of warrants to purchase convertible preferred stock, (vii) the determination of fair value of the Company’s common stock, (viii) the contingent consideration in a business acquisition, (ix) the fair value of the embedded derivative associated with the subordinated convertible note, (x) the determination of the valuation allowance and estimated tax benefit associated with deferred tax assets and net deferred tax liability, (xi) any impairment of long-lived assets including in-process technology and goodwill and (xii) legal contingencies. Actual results could differ from those estimates.
Concentration of Credit Risk	'
	Concentration of Credit Risk
	The Company is subject to credit risk from its accounts receivable which are derived from revenue earned from AlloMap tests provided for patients located in the U.S. and billed to various third-party payers. For the three months ended September 30, 2014 and 2013, 52% and 59%, respectively, of total revenue was derived from Medicare. For the nine months ended September 30, 2014 and 2013, 50% and 55%, respectively, of total revenue was derived from Medicare. No other payer represented more than 10% of testing revenue for these periods. At September 30, 2014, 63% of accounts receivable were from Medicare. No other payer represented more than 10% of accounts receivable at September 30, 2014.
Fair Value of Financial Instruments	'
	Fair Value of Financial Instruments
	Fair value is defined as the price that would be received from selling an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. When determining fair value, the Company considers the principal or most advantageous market in which the Company would transact, and it takes into consideration the assumptions that market participants would use when pricing the asset or liability. The Company’s assessment of the significance of a particular input to the fair value measurement of an asset or liability requires management to make judgments and to consider specific characteristics of that asset or liability.
	The carrying amounts of certain of the Company’s financial instruments, including cash equivalents, accounts receivable, accounts payable, and accrued liabilities, approximate fair value due to their short maturities. The carrying amount of the convertible preferred stock warrant liability and the subordinated convertible note equity call option liability (see Note 9) also represent their fair value.
Cash Equivalents	'
	Cash Equivalents
	The Company considers all highly liquid investments that are readily convertible into cash having maturities at the time of purchase of three months or less to be cash equivalents. Cash equivalents include money market funds, obligations of U.S. government agencies, and government-sponsored entities which are carried at fair value.
Testing Revenue	'
	Testing Revenue
	The Company recognizes revenues for tests delivered when the following criteria are met: (i) persuasive evidence that an arrangement exists; (ii) delivery has occurred or services rendered; (iii) the fee is fixed or determinable; and (iv) collectability is reasonably assured.
	The first criterion is satisfied when a third-party payer makes a coverage decision or enters into a contractual arrangement with the Company for the test. The second criterion is satisfied when the Company performs the test and delivers the test result to the ordering physician. The third criterion is satisfied if the third-party payer’s coverage decision or reimbursement contract specifies a price for the test. The fourth criterion is satisfied based on management’s judgments regarding the collectability of the fees charged under the arrangement. Such judgments include review of past payment history. AlloMap testing may be considered investigational by some payers and not covered under their reimbursement policies. Others may cover the test, but not pay a set or determinable amount. As a result, in the absence of a reimbursement agreement or sufficient payment history, collectability cannot reasonably be assured so revenue is not recognized at the time the test is delivered.
	If all criteria set forth above are met, revenue is recognized. When the first, third or fourth criteria are not met but third-party payers make a payment to the Company for tests performed, the Company recognizes revenue on the cash basis in the period in which the payment is received.
	Revenue is recognized on the accrual basis net of adjustments for differences between amounts billed and the estimated receipts from payers. The amount the Company expects to collect may be lower than the agreed upon amount due to several factors, such as the amount of patient co-payments, the existence of secondary payers and claim denials. Estimated receipts are based upon historical payment practices of payers. Differences between estimated and actual cash receipts are recorded as an adjustment to revenue, which have been immaterial to date.
Collaboration and License Revenue	'
	Collaboration and License Revenue
	The Company generates revenue from collaboration and license agreements. Collaboration and license agreements may include non-refundable upfront payments, partial or complete reimbursement of research and development costs, contingent payments based on the occurrence of specified events under the agreements, license fees and royalties on sales of products or product candidates if they are successfully commercialized. The Company’s performance obligations under the collaborations may include the transfer of intellectual property rights in the form of licenses, obligations to provide research and development services and obligations to participate on certain development committees with the collaboration partners. The Company makes judgments that affect the periods over which it recognizes revenue. The Company periodically reviews its estimated periods of performance based on the progress under each arrangement and accounts for the impact of any change in estimated periods of performance on a prospective basis.
	The Company recognizes contingent consideration received from the achievement of a substantive milestone in its entirety in the period in which the milestone is achieved, which the Company believes is more consistent with the substance of its performance under its various license and collaboration agreements. The Company did not recognize any milestones during the three months or nine month periods ended September 30, 2014 or 2013.
Cost of Testing	'
	Cost of Testing
	Cost of testing reflects the aggregate costs incurred in delivering the Company’s AlloMap test results to clinicians. The components of cost of testing are materials and service costs, direct labor costs, including stock-based compensation, equipment and infrastructure expenses associated with testing samples, shipping, logistics and specimen processing charges to collect and transport samples and allocated overhead including rent, information technology, equipment depreciation and utilities and royalties. Costs associated with performing tests (except royalties) are recorded as the test is processed regardless of whether and when revenue is recognized with respect to that test. As a result, our cost of testing as a percentage of revenue may vary significantly from period to period because we do not recognize all revenue in the period in which the associated costs are incurred. Royalties for licensed technology, calculated as a percentage of test revenues, are recorded as license fees in cost of testing at the time the test revenues are recognized.
Business Combinations	'
	Business Combinations
	In accordance with ASC 805, Business Combinations, the Company determines and allocates the purchase price of an acquired business to the tangible and identifiable intangible assets acquired and liabilities assumed based on their estimated fair values as of the business combination date, including identifiable intangible assets which either arise from a contractual or legal right or are separable from goodwill. The Company bases the estimated fair value of identifiable intangible assets acquired in a business combination on independent valuations that use information and assumptions provided by management, which consider management’s best estimates of inputs and assumptions that a market participant would use. The Company allocates any excess purchase price over the estimated fair value assigned to the net tangible and identifiable intangible assets acquired and liabilities assumed to goodwill. The use of alternative valuation assumptions, including estimated revenue projections, growth rates, royalty rates, cash flows, discount rates, estimated useful lives and probabilities surrounding the achievement of contingent milestones could result in different purchase price allocations and amortization expense in current and future periods.
	Goodwill and indefinite-lived intangible assets including acquired in-process technology are reviewed for impairment on an annual basis or more frequently if events or circumstances indicate that goodwill or indefinite-lived intangible assets may be impaired. The Company’s goodwill evaluation is based on both qualitative and quantitative assessments regarding the fair value of goodwill relative to its carrying value. The Company assesses qualitative factors to determine if its sole reporting unit’s fair value is more likely than not to exceed its carrying value, including goodwill. In the event the Company determines that it is more likely than not that its reporting unit’s fair value is less than its carrying amount, quantitative testing is performed comparing recorded values to estimated fair values. If the fair value exceeds the carrying value, goodwill is not impaired. If the carrying value exceeds the fair value, then the Company would calculate the potential impairment loss by comparing the implied fair value of goodwill with the carrying value. If the implied fair value of goodwill is less than the carrying value, then an impairment charge would be recorded. The Company performs its annual evaluation of goodwill during the fourth quarter of each fiscal year. Impairment losses on indefinite-lived intangible assets are recognized based solely on a comparison of the fair value of the asset to its carrying value, without consideration of any recoverability test.
	In those circumstances where an acquisition involves a contingent consideration arrangement that meets the definition of a liability under ASC 480, Distinguishing Liabilities from Equity, the Company recognizes a liability equal to the fair value of the contingent payments the Company expects to make as of the acquisition date. The Company remeasures this liability each reporting period and records changes in the fair value as a component of operating expenses.
	Transaction costs associated with these acquisitions are expensed as incurred in general and administrative expenses. Results of operations and cash flows of acquired companies are included in the Company’s operating results from the date of acquisition.
Stock-Based Compensation	'
	Stock–Based Compensation
	The Company uses the Black-Scholes valuation model, which requires the use of estimates such as stock price volatility and expected option lives, to value employee stock options. The Company estimates the expected option lives using historical data, volatility using data of similar companies in the diagnostics industry, and risk-free rates based on the implied yield currently available in the U.S. Treasury zero-coupon issues with a remaining term equal to the expected option lives, and dividend yield based on the Company’s historical data.
	The Company uses the straight-line attribution method for recognizing compensation expense. Compensation expense is recognized on awards ultimately expected to vest and reduced for forfeitures that are estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates. Forfeitures are estimated based on the Company’s historical experience.
	Equity instruments granted to nonemployees are valued using the Black-Scholes valuation model and are subject to periodic revaluation over their vesting terms. Nonemployee stock compensation is recognized upon vesting of the stock options which is commensurate with the period over which services are provided.
Impairment	'
	Impairment
	The Company evaluates its long-lived assets for indicators of possible impairment when events or changes in circumstances indicate the carrying amount of an asset may not be recoverable. The Company then compares the carrying amounts of the assets with the future net undiscounted cash flows expected to be generated by such asset. Should an impairment exist, the impairment loss would be measured based on the excess carrying value of the asset over the asset’s fair value determined using discounted estimates of future cash flows. The Company has not identified any such impairment losses to date.
Warrants	'
	Warrants
	At September 30, 2014, the Company had freestanding warrants enabling counterparties to purchase shares of its common stock. Prior to the Company’s initial public offering in July 2014, the Company also had freestanding warrants enabling counterparties to purchase shares of its convertible preferred stock. In accordance with the accounting guidance regarding distinguishing liabilities from equity, freestanding warrants for convertible preferred stock that are contingently redeemable are classified as liabilities on the balance sheets and are recorded at their estimated fair value. These warrants are remeasured at each balance sheet date, and any change in estimated fair value is recognized in other income (expense), net on the statements of operations. Prior to the IPO, the Company adjusted the liability for changes in estimated fair value until the earlier of the exercise or expiration of the warrants. Upon the IPO, certain preferred stock warrants were converted into warrants to purchase common stock, and, accordingly, the liability was reclassified to equity, while other warrants expired pursuant to their terms.
	The Company accounts for its warrants to purchase shares of common stock as equity in accordance with the accounting guidance distinguishing liabilities from equity.
Comprehensive Income (Loss)	'
	Comprehensive Income (Loss)
	Net income (loss) and comprehensive income (loss) are the same for all periods presented.
Recent Accounting Pronouncements	'
	Recent Accounting Pronouncements
	In May 2014, the Financial Accounting Standards Board issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606) (“ASU 2014-09”), which amends the existing accounting standards for revenue recognition. ASU 2014-09 is based on principles that govern the recognition of revenue at an amount an entity expects to be entitled to when products are transferred to customers. ASU 2014-09 will be effective for the Company beginning in its first quarter of 2017. Early adoption is not permitted. The new revenue standard may be applied retrospectively to each prior period presented or retrospectively with the cumulative effect recognized as of the date of adoption. The Company is currently evaluating the impact of adopting the new revenue standard on its financial statements.

Net_Income_Loss_Per_Share_Tabl

Net Income (Loss) Per Share (Tables)	9 Months Ended
	Sep. 30, 2014
Earnings Per Share [Abstract]	'
Computation of Basic and Diluted Net Income (Loss) Per Share	'
	The following tables set forth the computation of the Company’s basic and diluted net income (loss) per share (in thousands, except shares and per share data):
		Three Months Ended						Nine Months Ended
		September 30,						September 30,
		2014			2013			2014			2013
	Numerator:
	Net income (loss)	$	1,213		$	(830	)	$	786		$	(2,980	)
	Add: interest expense related to subordinated convertible note		231			—			364			—
	Less: gain on change in fair value of derivative related to subordinated convertible note		—			—			(118	)		—
	Less: gain on extinguishment of derivative related to subordinated convertible note		(120	)		—			(120	)		—
	Net income (loss) attributable to common stockholders	$	1,324		$	(830	)	$	912		$	(2,980	)
	Denominator:
	Weighted-average shares used to compute basic net income (loss) per share attributable to common stockholders		9,279,649			1,011,136			3,798,559			1,011,001
	Effect of potentially dilutive securities:
	Shares of common stock subject to conversion from preferred stock		1,446,313			—			3,973,622			—
	Shares of common stock subject to conversion from subordinated convertible note		122,142			—			179,614			—
	Shares of common stock subject to outstanding options		371,273			—			347,108			—
	Weighted-average shares used to compute diluted net income (loss) per share attributable to common stockholders		11,219,377			1,011,136			8,298,903			1,011,001
	Net income (loss) per share attributable to common stockholders:
	Basic	$	0.13		($	0.82	)	$	0.21		($	2.95	)
	Diluted	$	0.12		($	0.82	)	$	0.11		($	2.95	)
Potentially Dilutive Securities Excluded from Diluted Net Income (Loss) Per Share	'
	The following potentially dilutive securities have been excluded from diluted net income (loss) per share, because their effect would be antidilutive:
		Three Months Ended						Nine Months Ended
		September 30,						September 30,
		2014			2013			2014			2013
	Shares of common stock subject to conversion from preferred stock		—			5,160,085			—			5,160,085
	Shares of common stock subject to outstanding options		514,370			491,259			514,370			491,259
	Shares of common stock subject to outstanding warrants		266,586			623,803			266,586			623,803
	Total		780,956			6,275,147			780,956			6,275,147

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2014
Fair Value Disclosures [Abstract]	'
Fair Value of Financial Assets and Liabilities Measured on Recurring Basis	'
	The following table sets forth the fair value of the Company’s financial assets and liabilities measured on a recurring basis, as of September 30, 2014 and December 31, 2013 (in thousands):
		September 30, 2014
		Level 1			Level 2			Level 3			Total
	Assets
	Money market funds	$	38,964		$	—		$	—		$	38,964
	Liabilities
	Contingent consideration	$	—		$	—		$	1,037		$	1,037
	Total liabilities	$	—		$	—		$	1,037		$	1,037
		December 31, 2013
		Level 1			Level 2			Level 3			Total
	Assets
	Money market funds	$	5,204		$	—		$	—		$	5,204
	Liabilities
	Warrants to purchase convertible preferred stock	$	—		$	—		$	525		$	525
	Total liabilities	$	—		$	—		$	525		$	525
Estimated Fair Value of Convertible Preferred Stock Warrant Liability Determined Using Black-Scholes Option Pricing Model	'
	The estimated fair value of the convertible preferred stock warrant liability as of December 31, 2013 was determined using the Black-Scholes option pricing model using the following assumptions:
	Estimated fair value of common stock	$	12.4
	Risk-free interest rate		0.8% - 2.1%
	Volatility		40% - 45%
	Estimated term equal to the remaining contractual term		3.3 - 5.6 years
	Expected dividend yield		—
Summary of Issuances, Changes in Fair Value and Reclassifications of Level 3 Financial Instruments	'
	The following table presents the issuances, changes in fair value and reclassifications of the Company’s Level 3 financial instruments that are measured at fair value on a recurring basis (in thousands):
		Level 3
		Contingent			Warrants			Derivative			Total
		Consideration			to Purchase			Liability
		Liability			Convertible			Related to
					Preferred			Subordinated
					Stock			Convertible
								Note
	Balance as of December 31, 2013	$	—		$	525		$	—		$	525
	Issuance of financial instruments		2,313			—			239			2,552
	Change in estimated fair value		(1,276	)		14			(239	)		(1,501	)
	Reclassification to stockholders’ equity		—			(539	)		—			(539	)
	Balance as of September 30, 2014	$	1,037		$	—		$	—		$	1,037

Inventory_Tables

Inventory (Tables)	9 Months Ended
	Sep. 30, 2014
Inventory Disclosure [Abstract]	'
Summary of Inventory	'
	The following table summarizes the Company’s inventory (in thousands):
		September 30,		December 31,
		2014		2013
	Finished goods	$	234	$	230
	Raw materials		262		288
	Total inventory	$	496	$	518

Accrued_and_Other_Liabilities_

Accrued and Other Liabilities (Tables)	9 Months Ended
	Sep. 30, 2014
Payables and Accruals [Abstract]	'
Components of Accrued and Other Liabilities	'
	The following table represents the components of accrued and other liabilities (in thousands):
		September 30,		December 31,
		2014		2013
	Accrued professional fees	$	391	$	175
	Accrued test sample processing fees		260		195
	Consideration payable in connection with business combination		194		—
	Deferred rent – current portion		187		145
	Accrued clinical studies		135		84
	Accrued overpayments and refunds		98		215
	Accrued interest		98		—
	Capital leases – current portion		79		43
	Other accrued expenses		469		191
		$	1,911	$	1,048

Stock_Option_Plans_Tables

Stock Option Plans (Tables)	9 Months Ended
	Sep. 30, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Summary of Option Activity and Related Information	'
	The following table summarizes option activity and related information during the nine months ended September 30, 2014 under the 2014 Equity Incentive Plan, the ImmuMetrix 2013 Equity Incentive Plan and the 2008 Plan and for options that remain outstanding under such plans:
		Nine Months Ended
		30-Sep-14
					Options Outstanding
		Shares			Number of			Weighted-
		Available			Shares			average
		for Grant						Exercise
								Price
	Beginning balance		332,995			466,965		$	1.99
	Increase in shares reserved for issuance		940,884			—		$	—
	Granted		(530,570	)		530,570		$	12.1
	Assumed in business combination		—			23,229		$	2.06
	Exercised		—			(3,038	)	$	2.04
	Forfeited		18,983			(18,983	)	$	10.31
	Expired		12,638			(12,638	)	$	2.85
	Ending balance		774,930			986,105		$	7.41
Summary of Options Outstanding and Exercisable Vested or Expected to Vest	'
	Options outstanding and exercisable that have vested or are expected to vest as of September 30, 2014 are as follows:
		Number			Weighted-			Weighted-			Aggregate
		of Shares			average			average			Intrinsic
					Exercise			Remaining			Value(in
					Price			Contractual			thousands)
								Life(Years)
	Vested		389,976		$	2.69			6.17		$	1,775
	Expected to vest		596,129		$	10.51			9.31		$	593
	Total		986,105		$	7.41			8.07		$	2,368
Summary of Expense Relating to Employee and Nonemployee Stock-Based Payment Awards	'
	The Company’s results of operations include expense relating to employee and nonemployee stock-based payment awards as follows (in thousands):
		Three Months Ended						Nine Months Ended
		September 30,						September 30,
		2014			2013			2014			2013
	Cost of testing	$	6		$	1		$	15		$	3
	Research and development		35			2			57			6
	Sales and marketing		13			—			22			2
	General and administrative		111			16			256			46
		$	165		$	19		$	350		$	57
Weighted-Average Assumptions Used to Fair Value of Stock-Based Awards	'
	The fair value of stock-based awards was estimated using the Black-Scholes option-pricing model using the following weighted-average assumptions:
		Three Months Ended						Nine Months Ended
		September 30,						September 30,
		2014			2013			2014			2013
	Risk-free interest rate		2.05	%		1.72	%		1.76	%		1.09	%
	Volatility		43.81	%		45.03	%		42.3	%		45.37	%
	Expected term, in years		6			6			5.3			6
	Expected dividend yield		0	%		0	%		0	%		0	%

Business_Combination_Tables

Business Combination (Tables)	9 Months Ended
	Sep. 30, 2014
Business Combinations [Abstract]	'
Schedule of Pro Forma Results of Operations	'
	The following table presents pro forma results of operations and gives effect to the IMX transaction as if the transaction had been consummated on January 1, 2013. The unaudited pro forma results of operations have been prepared for comparative purposes only and are not necessarily indicative of what would have occurred had the business combination been completed at the beginning of the period or of the results that may occur in the future. Furthermore, the pro forma financial information does not reflect the impact of any reorganization or operating efficiencies resulting from combining the two companies (in thousands, except per share data).
		Nine Months Ended
		September 30,
		2014			2013
	Net revenue	$	19,354		$	16,243
	Net income (loss)	$	(1,075	)	$	(2,904	)
	Net income (loss) per common share - basic	$	(0.28	)	$	(2.87	)
	Net income (loss) per common share - diluted	$	(0.28	)	$	(2.87	)

Organization_Additional_Inform

Organization - Additional Information (Detail) (USD $)

0 Months Ended

1 Months Ended

9 Months Ended

0 Months Ended

0 Months Ended

9 Months Ended

Aug. 13, 2014

Jul. 22, 2014

Jul. 31, 2013

Sep. 30, 2014

Sep. 30, 2013

Dec. 31, 2013

Jul. 22, 2014

Jul. 22, 2014

Jul. 22, 2014

Jul. 22, 2014

Jul. 01, 2014

Sep. 30, 2014

Jul. 22, 2014

Jul. 01, 2014

Segment

IPO [Member]

IPO [Member]

Common Stock [Member]

Convertible Subordinated Debt [Member]

Amendment [Member]

Amendment [Member]

Amendment [Member]

Amendment [Member]

Schedule of Capitalization, Equity [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of operating segment

'

'

'

1

'

'

'

'

'

'

'

'

'

'

Common stock shares issued from IPO

'

'

'

'

'

'

4,000,000

'

'

'

'

'

'

'

Issuance of additional shares pursuant to exercise of underwriters' overallotment option

220,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Public offering price per share

'

'

'

'

'

'

'

$10

'

'

'

'

'

'

Underwriting discounts and commissions

'

'

'

$3,716,000

$0

'

$3,000,000

'

'

'

'

'

'

'

Proceeds from initial public offering net of underwriting discounts and commissions

'

'

'

39,246,000

0

'

39,200,000

'

'

'

'

'

'

'

Offering expenses

'

'

'

'

'

'

3,800,000

'

'

'

'

'

'

'

Net proceeds from issuance of initial public offering

'

'

467,000

'

'

'

35,500,000

'

'

'

'

'

'

'

Shares issued upon conversion

'

510,777

'

'

'

'

'

'

6,048,220

510,777

'

'

'

'

Convertible note principal amount

'

'

'

'

'

'

'

'

'

$5,000,000

'

'

'

'

Reverse stock split, ratio

'

'

'

'

'

'

'

'

'

'

0.145985401

'

'

'

Reverse stock split

'

'

'

'

'

'

'

'

'

'

'1 for 6.85

'

'

'

Common stock, shares authorized

'

'

'

100,000,000

'

7,737,226

'

'

'

'

'

'

100,000,000

10,000,000

Reverse Stock Split effective date

'

'

'

'

'

'

'

'

'

'

'

14-Jul-14

'

'

Common stock, par value

'

'

'

$0.00

'

$0.00

'

'

'

'

'

'

$0.00

'

Convertible preferred stock, shares authorized

'

'

'

0

'

6,417,954

'

'

'

'

'

'

10,000,000

'

Convertible preferred stock, par value

'

'

'

$0.00

'

$0.00

'

'

'

'

'

'

$0.00

'

Summary_of_Significant_Account1

Summary of Significant Accounting Policies - Additional Information - Concentration of Credit Risk (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Services Revenue [Member] | Customer Concentration Risk [Member] | Minimum [Member]	'	'	'	'
Concentration Risk [Line Items]	'	'	'	'
Concentration risk, percentage	10.00%	10.00%	10.00%	10.00%
Services Revenue [Member] | Customer Concentration Risk [Member] | Medicare [Member]	'	'	'	'
Concentration Risk [Line Items]	'	'	'	'
Concentration risk, percentage	52.00%	59.00%	50.00%	55.00%
Accounts Receivable [Member] | Credit Concentration Risk [Member] | Minimum [Member]	'	'	'	'
Concentration Risk [Line Items]	'	'	'	'
Concentration risk, percentage	'	'	10.00%	'
Accounts Receivable [Member] | Credit Concentration Risk [Member] | Medicare [Member]	'	'	'	'
Concentration Risk [Line Items]	'	'	'	'
Concentration risk, percentage	'	'	63.00%	'

Summary_of_Significant_Account2

Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Accounting Policies [Abstract]	'	'	'	'
Cash equivalents maturity, description	'	'	'The Company considers all highly liquid investments that are readily convertible into cash having maturities at the time of purchase of three months or less to be cash equivalents.	'
Revenue recognition under milestone method	$0	$0	$0	$0

Net_Income_Loss_Per_Share_Comp

Net Income (Loss) Per Share - Computation of Basic and Diluted Net Income (Loss) Share (Detail) (USD $)	3 Months Ended			9 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2014	Jun. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Numerator:	'	'	'	'	'
Net income (loss)	$1,213	'	($830)	$786	($2,980)
Add: interest expense related to subordinated convertible note	231	'	0	364	0
Less: gain on change in fair value of derivative related to subordinated convertible note	0	119	0	-118	0
Less: gain on extinguishment of derivative related to subordinated convertible note	-120	'	0	-120	0
Net income (loss) attributable to common stockholders	$1,324	'	($830)	$912	($2,980)
Denominator:	'	'	'	'	'
Weighted-average shares used to compute basic net income (loss) per share attributable to common stockholders	9,279,649	'	1,011,136	3,798,559	1,011,001
Effect of potentially dilutive securities:	'	'	'	'	'
Shares of common stock subject to conversion from preferred stock	1,446,313	'	0	3,973,622	0
Shares of common stock subject to conversion from subordinated convertible note	122,142	'	0	179,614	0
Shares of common stock subject to outstanding options	371,273	'	0	347,108	0
Weighted-average shares used to compute diluted net income (loss) per share attributable to common stockholders	11,219,377	'	1,011,136	8,298,903	1,011,001
Basic	$0.13	'	($0.82)	$0.21	($2.95)
Diluted	$0.12	'	($0.82)	$0.11	($2.95)

Net_Income_Loss_Per_Share_Pote

Net Income (Loss) Per Share - Potentially Dilutive Securities Excluded from Diluted Net Income (Loss) Per Share (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'	'
Potential dilutive securities excluded from diluted net income (loss) per share attributable to common stockholders, Total	780,956	6,275,147	780,956	6,275,147
Shares of common stock subject to conversion from preferred stock [Member]	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'	'
Potential dilutive securities excluded from diluted net income (loss) per share attributable to common stockholders, Total	0	5,160,085	0	5,160,085
Shares of common stock subject to outstanding options [Member]	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'	'
Potential dilutive securities excluded from diluted net income (loss) per share attributable to common stockholders, Total	514,370	491,259	514,370	491,259
Shares of common stock subject to outstanding warrants [Member]	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'	'
Potential dilutive securities excluded from diluted net income (loss) per share attributable to common stockholders, Total	266,586	623,803	266,586	623,803

Fair_Value_Measurements_Fair_V

Fair Value Measurements - Fair Value of Financial Assets and Liabilities Measured on Recurring Basis (Detail) (Recurring [Member], USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Assets	'	'
Money market funds	$38,964	$5,204
Liabilities	'	'
Contingent consideration	1,037	'
Warrants to purchase convertible preferred stock	'	525
Total liabilities	1,037	525
Fair Value Measured Using - Level 1 [Member]	'	'
Assets	'	'
Money market funds	38,964	5,204
Liabilities	'	'
Contingent consideration	0	'
Warrants to purchase convertible preferred stock	'	0
Total liabilities	0	0
Fair Value Measured Using - Level 2 [Member]	'	'
Assets	'	'
Money market funds	0	0
Liabilities	'	'
Contingent consideration	0	'
Warrants to purchase convertible preferred stock	'	0
Total liabilities	0	0
Fair Value Measured Using - Level 3 [Member]	'	'
Assets	'	'
Money market funds	0	0
Liabilities	'	'
Contingent consideration	1,037	'
Warrants to purchase convertible preferred stock	'	525
Total liabilities	$1,037	$525

Fair_Value_Measurements_Additi

Fair Value Measurements - Additional Information (Detail) (USD $)

3 Months Ended

9 Months Ended

0 Months Ended

9 Months Ended

0 Months Ended

1 Months Ended

0 Months Ended

9 Months Ended

Sep. 30, 2014

Jun. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Apr. 17, 2014

Sep. 30, 2014

Sep. 30, 2014

Jun. 30, 2014

Apr. 17, 2014

Jul. 31, 2014

Sep. 30, 2014

Sep. 30, 2014

Illumina, Inc. [Member]

ImmuMetrix, Inc. [Member]

ImmuMetrix, Inc. [Member]

IPO [Member]

IPO [Member]

IPO [Member]

Contingent consideration [Member]

Contingent consideration [Member]

CommercialTests

CommercialTests

ImmuMetrix, Inc. [Member]

ImmuMetrix, Inc. [Member]

Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

Transfers between Level 1, Level 2 and Level 3 categories during the periods

'

'

'

$0

'

'

'

'

'

'

'

'

'

Contingent obligation to issue common stock

'

'

'

'

'

'

'

'

'

'

'

227,845

'

Number of commercial tests involving the measurement of cfDNA to be completed

'

'

'

'

'

'

2,500

2,500

'

'

'

'

'

Milestone description

'

'

'

'

'

'

'

'The milestone will be achieved if the Company completes 2,500 commercial tests involving the measurement of cfDNA in organ transplant recipients in the United States no later than six years after the closing date of the acquisition.

'

'

'

'

'The issuance will occur if the Company completes 2,500 commercial tests involving the measurement of cfDNA in organ transplant recipients in the United States by June 10, 2020.

Probability of the achievement

'

'

'

'

'

'

'

'

'

'

'

65.00%

'

Contingent consideration maturity date

'

'

'

'

'

'

'

10-Jun-20

'

'

'

'

'

Subordinated convertible promissory note issued

'

'

'

'

'

5,000,000

'

'

'

'

'

'

'

Change in control for repayment

'

'

'

'

'

'

'

'

5.00%

10.00%

'

'

'

Estimated fair value of embedded derivative liabilities

'

239,000

'

'

'

'

'

'

'

'

'

'

'

Fair value of derivative

'

120,000

'

'

'

'

'

'

'

'

0

'

'

Gain on derivative

$0

$119,000

$0

($118,000)

$0

'

'

'

'

'

$120,000

'

'

Fair_Value_Measurements_Estima

Fair Value Measurements - Estimated Fair Value of Convertible Preferred Stock Warrant Liability Determined Using Black-Scholes Option Pricing Model (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Sep. 30, 2014
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]	'	'
Estimated fair value of common stock	$12.40	$7
Expected dividend yield	0.00%	'
Minimum [Member]	'	'
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]	'	'
Risk-free interest rate	0.80%	'
Volatility	40.00%	'
Estimated term equal to the remaining contractual term	'3 years 3 months 18 days	'
Maximum [Member]	'	'
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]	'	'
Risk-free interest rate	2.10%	'
Volatility	45.00%	'
Estimated term equal to the remaining contractual term	'5 years 7 months 6 days	'

Fair_Value_Measurements_Summar

Fair Value Measurements - Summary of Issuances, Changes in Fair Value and Reclassifications of Level 3 Financial Instruments (Detail) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014
Significant Unobservable Inputs (Level 3) [Line Items]	'
Balance as of December 31, 2013	$525
Issuance of financial instruments	2,552
Change in estimated fair value	-1,501
Reclassification to stockholders' equity	-539
Balance as of September 30, 2014	1,037
Significant Unobservable Inputs (Level 3), Warrants to Purchase Convertible Preferred Stock [Member]	'
Significant Unobservable Inputs (Level 3) [Line Items]	'
Balance as of December 31, 2013	525
Issuance of financial instruments	0
Change in estimated fair value	14
Reclassification to stockholders' equity	-539
Balance as of September 30, 2014	0
Significant Unobservable Inputs (Level 3), Derivative Liability Related to Subordinated Convertible Note [Member]	'
Significant Unobservable Inputs (Level 3) [Line Items]	'
Balance as of December 31, 2013	0
Issuance of financial instruments	239
Change in estimated fair value	-239
Reclassification to stockholders' equity	0
Balance as of September 30, 2014	0
Significant Unobservable Inputs (Level 3), Contingent Consideration Liability [Member]	'
Significant Unobservable Inputs (Level 3) [Line Items]	'
Balance as of December 31, 2013	0
Issuance of financial instruments	2,313
Change in estimated fair value	-1,276
Reclassification to stockholders' equity	0
Balance as of September 30, 2014	$1,037

Inventory_Summary_of_Inventory

Inventory - Summary of Inventory (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Inventory Disclosure [Abstract]	'	'
Finished goods	$234	$230
Raw materials	262	288
Total inventory	$496	$518

Accrued_and_Other_Liabilities_1

Accrued and Other Liabilities - Components of Accrued and Other Liabilities (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Payables and Accruals [Abstract]	'	'
Accrued professional fees	$391	$175
Accrued test sample processing fees	260	195
Consideration payable in connection with business combination	194	0
Deferred rent - current portion	187	145
Accrued clinical studies	135	84
Accrued overpayments and refunds	98	215
Accrued interest	98	0
Capital leases - current portion	79	43
Other accrued expenses	469	191
Total accrued and other liabilities	$1,911	$1,048

Commitments_and_Contingencies_

Commitments and Contingencies - Additional Information (Detail) (USD $)

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

6 Months Ended

9 Months Ended

12 Months Ended

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Dec. 31, 2013

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 11, 2014

Dec. 31, 2011

Sep. 30, 2014

Dec. 31, 2013

Dec. 31, 2012

July 1, 2011 through June 30, 2014 [Member]

July 1, 2011 through June 30, 2014 [Member]

Unpaid Royalties [Member]

Unpaid Royalties [Member]

AlloMap [Member]

AlloMap [Member]

AlloMap [Member]

AlloMap [Member]

July 1, 2011 through June 30, 2014 [Member]

July 1, 2011 through June 30, 2014 [Member]

July 1, 2011 through June 30, 2014 [Member]

July 1, 2011 through June 30, 2014 [Member]

July 1, 2011 through June 30, 2014 [Member]

Loss Contingencies [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

Settlement and mutual release agreement, counter party name

'

'

'

'

'

'

'

'Roche

'

'

'

'

'

Settlement and mutual release agreement, date

'

'

'

'

'

'

'

'September 11, 2014

'

'

'

'

'

Past due royalties

$0

'

$0

'

$2,804,000

'

'

'

$2,827,220

'

'

'

'

Maximum number of days from end of calendar quarter for royalty payment

'

'

'

'

'

'

'

'45 days

'

'

'

'

'

Settlement and mutual release agreement, terms of agreement

'

'

'

'

'

'

'

'On September 11, 2014, the Company entered into a settlement and mutual release agreement with Roche whereby: (i) for the period beginning July 1, 2011 through June 30, 2014, the Company agreed to pay the amount of $2,827,220 in settlement of past royalties due; (ii) for the period beginning July 1, 2014 through September 30, 2014, the Company agreed to pay royalties based on the same combination services percentage used to determine the past royalties due; (iii) for the period beginning October 1, 2014 through September 30, 2017, Roche and the Company agreed to a downward adjustment of the combination services percentage used to determine the portion of the AlloMap testing revenue that is royalty bearing under the terms of the license; (iv) the Company agreed to report and pay quarterly royalties within 45 days of the end of each calendar quarter; (v) Roche agreed that, subject to the Companybs timely payment of all applicable royalties through such date, no further royalties will be payable by the Company for periods after September 30, 2017;

'

'

'

'

'

Settlement and payment

'

'

'

'

'

'

2,800,000

'

'

'

'

'

'

Decrease in cost of testing

'

'

'

'

'

566,000

566,000

'

'

'

'

'

'

Decrease in interest expense

'

'

'

'

'

132,000

132,000

'

'

'

'

'

'

Royalty revenues

$49,000

$27,000

$167,000

$57,000

'

'

'

'

'

$400,000

$500,000

$1,000,000

$900,000

Collaboration_and_Licensing_Ag1

Collaboration and Licensing Agreements - Additional Information (Detail)

1 Months Ended

3 Months Ended

9 Months Ended

12 Months Ended

0 Months Ended

1 Months Ended

3 Months Ended

9 Months Ended

Jul. 31, 2013

Jun. 30, 2013

Jun. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Dec. 31, 2012

Dec. 31, 2013

Sep. 30, 2014

Sep. 18, 2014

Apr. 30, 2012

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Jun. 30, 2013

Jun. 30, 2013

USD ($)

USD ($)

EUR (€)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

Up-front Payment Arrangement [Member]

Laboratory Corp of America Holdings [Member]

Laboratory Corp of America Holdings [Member]

Laboratory Corp of America Holdings [Member]

Laboratory Corp of America Holdings [Member]

Laboratory Corp of America Holdings [Member]

Laboratory Corp of America Holdings [Member]

Laboratory Corp of America Holdings [Member]

Diaxonhit (DHT) [Member]

Diaxonhit (DHT) [Member]

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

Scenario, Forecast [Member]

USD ($)

EUR (€)

USD ($)

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Consideration of arrangement of license

'

'

'

'

'

'

'

'

'

'

'

$1,000,000

'

'

'

'

'

'

'

Description of agreement expire term

'

'

'

'

'

'The agreement will expire at the later of the last-to-expire patent in the EEA or ten years from the first commercial sale of the test in the EEA, which is expected to occur in late 2014 or early 2015.

'

'

'

'

'

'

'

'

'The license term in the 2012 Agreement was the later of 10 years from the date of the agreement or the expiration of the last-to-expire patents and patent applications included in the CareDx technology licensed to LabCorp, unless the license were terminated by mutual agreement.

'

'

'

'

Upfront license fee payment

'

'

'

'

'

'

'

1,000,000

'

'

'

'

'

'

'

'

'

'

'

Non-refundable and non creditable payment received

'

'

'

'

'

'

'

250,000

'

'

'

'

'

'

'

'

'

'

'

Termination of collaboration agreement date

'

'

'

'

'

'

'

'

'

'

'

'

'

'

18-Sep-14

'

'

'

'

Research and development expenses

'

'

'

1,036,000

668,000

2,548,000

2,516,000

'

'

'

500,000

'

0

34,000

32,000

318,000

'

'

'

Portion of upfront license fee included in current deferred revenue

'

'

'

673,000

'

673,000

'

'

80,000

611,000

'

'

'

'

'

'

'

'

'

Termination agreement fee

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

500,000

'

'

Revenue recognized under collaboration and licensing agreements

'

'

'

0

64,000

31,000

331,000

'

'

'

'

'

'

'

'

'

'

'

'

Amortization of upfront license fee

'

'

'

0

47,000

15,000

172,000

'

'

'

'

'

'

'

'

'

'

'

'

Reimbursement of research and development expenses

'

'

'

0

17,000

16,000

159,000

'

'

'

'

'

'

'

'

'

'

'

'

Upfront cash payment

'

503,000

387,500

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Refundable upfront payments

'

344,000

250,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Common stock value

'

'

'

12,000

'

12,000

'

'

1,000

'

'

'

'

'

'

'

'

503,000

387,500

Shares sold for consideration

467,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Royalty revenues

'

'

'

49,000

27,000

167,000

57,000

'

'

'

'

'

'

'

'

'

'

'

'

Royalty revenues receivable balance

'

'

'

$49,000

'

$49,000

'

'

$37,000

'

'

'

'

'

'

'

'

'

'

Subordinated_Convertible_Note_

Subordinated Convertible Note - Additional Information (Detail) (USD $)	0 Months Ended	1 Months Ended	3 Months Ended	9 Months Ended
	Jul. 22, 2014	Jul. 22, 2014	Jun. 30, 2014	Sep. 30, 2014	Sep. 30, 2014	Apr. 17, 2014
					Illumina, Inc. [Member]	Illumina, Inc. [Member]
Debt Instrument [Line Items]	'	'	'	'	'	'
Subordinated convertible promissory note issued	'	'	'	'	'	$5,000,000
Subordinated convertible promissory note annual interest rate	'	'	'	9.95%	'	8.00%
Subordinated convertible promissory note maturity term	'	'	'	'	'1 year	'
Initial Public offering, closing date	'	'	'	22-Jul-14	'	'
Shares issued upon conversion	510,777	'	'	'	'	'
Amortization of debt discount	'	205,000	51,000	'	'	'
Extinguishment of embedded derivative	'	'	'	$120,000	'	'

Stock_Option_Plans_Additional_

Stock Option Plans - Additional Information (Detail) (USD $)	9 Months Ended		0 Months Ended	9 Months Ended
In Millions, except Share data, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Jan. 01, 2014	Sep. 30, 2014	Jan. 01, 2014
			2014 Equity Incentive Plan [Member]	2014 Equity Incentive Plan [Member]	2014 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'	'
Shares reserved for issuance of common stock	'	'	'	838,695	357,075
Maximum number of shares may be added to the plan hereunder	'	'	'	865,252	'
Outstanding shares of common stock, in percentage	'	'	4.00%	'	'
Weighted-average grant-date fair value of options granted during the period	$5.07	'	'	'	'
Common stock price per share	$7	$12.40	'	'	'
Total unrecognized stock-based compensation related to nonvested employee stock option awards granted	$2.30	'	'	'	'
Remaining vesting period	'3 years 1 month 6 days	'	'	'	'

Stock_Option_Plans_Summary_of_

Stock Option Plans - Summary of Option Activity and Related Information (Detail) (USD $)	9 Months Ended
	Sep. 30, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Shares Available for Grant, Beginning Balance	332,995
Shares Available for Grant, Increase in shares reserved for issuance	940,884
Shares Available for Grant, Granted	-530,570
Shares Available for Grant, Assumed in business combination	'
Shares Available for Grant, Exercised	0
Shares Available for Grant, Forfeited	18,983
Shares Available for Grant, Expired	12,638
Shares Available for Grant, Ending Balance	774,930
Number of Shares, Beginning Balance	466,965
Number of Shares, Increase in shares reserved for issuance	0
Number of Shares, Granted	530,570
Number of Shares, Assumed in business combination	23,229
Number of Shares, Exercised	-3,038
Number of Shares, Forfeited	-18,983
Number of Shares, Expired	-12,638
Number of Shares, Ending Balance	986,105
Weighted-average Exercise Price, Beginning Balance	$1.99
Weighted-average Exercise Price, Increase in shares reserved for issuance	$0
Weighted-average Exercise Price, Granted	$12.10
Weighted-average Exercise Price, Assumed in business combination	$2.06
Weighted-average Exercise Price, Exercised	$2.04
Weighted-average Exercise Price, Forfeited	$10.31
Weighted-average Exercise Price, Expired	$2.85
Weighted-average Exercise Price, Ending Balance	$7.41

Stock_Option_Plans_Summary_of_1

Stock Option Plans - Summary of Options Outstanding and Exercisable Vested or Expected to Vest (Detail) (USD $)	9 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Number of Shares, Vested	389,976
Number of Shares, Expected to vest	596,129
Number of Shares, Total	986,105
Weighted-average Exercise Price, Vested	$2.69
Weighted-average Exercise Price, Expected to vest	$10.51
Weighted-average Exercise Price, Total	$7.41
Weighted-average Remaining Contractual Life (Years), Vested	'6 years 2 months 1 day
Weighted-average Remaining Contractual Life (Years), Expected to vest	'9 years 3 months 22 days
Weighted-average Remaining Contractual Life (Years), Total	'8 years 26 days
Aggregate Intrinsic Value, Vested	$1,775
Aggregate Intrinsic Value, Expected to vest	593
Aggregate Intrinsic Value, Total	$2,368

Stock_Option_Plans_Summary_of_2

Stock Option Plans - Summary of Expense Relating to Employee and Nonemployee Stock-Based Payment Awards (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]	'	'	'	'
Share based compensation, Total expensed	$165	$19	$350	$57
Cost of testing [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]	'	'	'	'
Share based compensation, Total expensed	6	1	15	3
Research and development [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]	'	'	'	'
Share based compensation, Total expensed	35	2	57	6
Sales and marketing [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]	'	'	'	'
Share based compensation, Total expensed	13	0	22	2
General and administrative [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]	'	'	'	'
Share based compensation, Total expensed	$111	$16	$256	$46

Stock_Option_Plans_WeightedAve

Stock Option Plans - Weighted-Average Assumptions Used to Fair Value of Stock-Based Awards (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'	'	'	'
Risk-free interest rate	2.05%	1.72%	1.76%	1.09%
Volatility	43.81%	45.03%	42.30%	45.37%
Expected term, in years	'6 years	'6 years	'5 years 3 months 18 days	'6 years
Expected dividend yield	0.00%	0.00%	0.00%	0.00%

Business_Combination_Additiona

Business Combination - Additional Information (Detail) (USD $)

9 Months Ended

0 Months Ended

9 Months Ended

0 Months Ended

9 Months Ended

0 Months Ended

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Jun. 10, 2014

Sep. 30, 2014

Sep. 30, 2013

Jun. 10, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Jun. 10, 2014

Sep. 30, 2014

Jun. 30, 2014

Jun. 10, 2014

Jun. 10, 2014

ImmuMetrix, Inc. [Member]

ImmuMetrix, Inc. [Member]

ImmuMetrix, Inc. [Member]

ImmuMetrix, Inc. [Member]

ImmuMetrix, Inc. [Member]

ImmuMetrix, Inc. [Member]

ImmuMetrix, Inc. [Member]

ImmuMetrix, Inc. [Member]

ImmuMetrix, Inc. [Member]

ImmuMetrix, Inc. [Member]

ImmuMetrix, Inc. [Member]

ImmuMetrix, Inc. [Member]

ImmuMetrix, Inc. [Member]

CommercialTests

CommercialTests

Contingent consideration [Member]

Contingent consideration [Member]

CareDx, Inc [Member]

Series G Preferred Stock [Member]

Series G Preferred Stock [Member]

Series G Preferred Stock [Member]

Series G Preferred Stock [Member]

Series G Preferred Stock [Member]

Contingent consideration [Member]

Contingent consideration [Member]

Contingent consideration [Member]

Stock Options [Member]

Business Acquisition [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Acquisition date

'

'

'

'

10-Jun-14

'

'

'

'

'

'

'

'

'

'

Estimated purchase price

'

'

'

$17,200,000

'

'

'

'

'

'

'

'

'

'

'

Business acquisition purchase price, cash

'

'

'

'

'

'

600,000

'

'

'

'

'

'

'

'

Shares issued, shares issuable upon achievement of future milestone, and options assumed

'

'

'

'

'

'

'

227,845

'

'

911,364

'

'

227,845

23,229

Estimated fair value

'

'

'

'

'

'

'

'

'

'

14,200,000

1,000,000

2,300,000

2,300,000

369,000

Milestone description

'

'

'

'

'The milestone will be achieved if the Company completes 2,500 commercial tests involving the measurement of cfDNA in organ transplant recipients in the United States no later than six years after the closing date of the acquisition.

'

'

'

'The issuance will occur if the Company completes 2,500 commercial tests involving the measurement of cfDNA in organ transplant recipients in the United States by June 10, 2020.

'

'

'

'

'

'

Number of commercial tests involving the measurement of cfDNA to be completed

'

'

2,500

'

2,500

'

'

'

'

'

'

'

'

'

'

Milestone measurement period

'

'

'

'

'6 years

'

'

'

'

'

'

'

'

'

'

Acquisition-related costs

'

'

'

'

'

'

'

'

'

1,700,000

'

'

'

'

'

Stock-based compensation

350,000

57,000

'

'

'

'

'

'

'

200,000

'

'

'

'

'

Business combination pro forma removal (addition) in income tax benefit

'

'

'

'

$1,500,000

$1,500,000

'

'

'

'

'

'

'

'

'

Business_Combination_Schedule_

Business Combination - Schedule of Pro Forma Results of Operations (Detail) (ImmuMetrix, Inc. [Member], USD $)	9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
ImmuMetrix, Inc. [Member]	'	'
Business Acquisition [Line Items]	'	'
Net revenue	$19,354	$16,243
Net income (loss)	($1,075)	($2,904)
Net income (loss) per common share - basic	($0.28)	($2.87)
Net income (loss) per common share - diluted	($0.28)	($2.87)

Debt_Additional_Information_De

Debt - Additional Information (Detail) (USD $)	1 Months Ended	9 Months Ended
	Aug. 31, 2013	Sep. 30, 2014	Aug. 31, 2012
Debt Instrument [Line Items]	'	'	'
Loan and security agreement cost	'	'	$15,000,000
Loan to defer the beginning of principal repayment	1-Mar-14	'	'
Loan interest description	'	'interest-only payments for 18 months through February 28, 2014 followed by 30 equal monthly principal and interest payments	'
Interest payment	'	566,822	'
Annual interest rate	'	9.95%	'
Facility Fee amount	'	75,000	'
Loan deferral additional fee	'	150,000	'
Final payment due at the end of the term	'	$1,275,000	'
Series G convertible preferred stock [Member]	'	'	'
Debt Instrument [Line Items]	'	'	'
Warrants to purchase stock of convertible preferred stock, shares	'	167,181	'
Warrants to purchase stock of convertible preferred stock, per share	'	$21.78	'
Warrants exercisable period	'	'The warrants are exercisable until 2019.	'

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Income Tax Disclosure [Abstract]	'	'	'	'
Income tax benefit	$0	$0	$1,500	$0