Description of Business and Summary of Significant Accounting Policies - Additional Information (Details)			1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Oct. 30, 2020 USD ($) $ / shares shares	Oct. 19, 2020	Oct. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) segment	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Cash and cash equivalents				$ 6,348,000		$ 6,348,000		$ 5,286,000
Accumulated deficit				257,681,000		257,681,000		230,864,000
Stockholders’ deficit				255,176,000	$ 222,059,000	$ 255,176,000	$ 222,059,000	228,539,000	$ 246,445,000	$ 238,234,000	$ 212,519,000	$ 205,713,000	$ 198,030,000
Number of operating segments | segment						1
Comprehensive loss						$ 0	0
Allowance for doubtful accounts				200,000		200,000		200,000
Impairment of long-lived assets						0	0
Goodwill impairments loss				0	$ 0	0	$ 0
Deferred revenue				5,673,000		$ 5,673,000		1,283,000
Patent
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Finite-lived intangible asset, useful life						10 years
Developed Technology
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Finite-lived intangible asset, useful life						9 years
Minimum
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, useful Lives						3 years
Maximum
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, useful Lives						5 years
Other Current Assets
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Restricted cash				200,000		$ 200,000		200,000
Inventory balances				3,200,000		3,200,000		800,000
Deferred offering costs				1,400,000		1,400,000		0
Money Market Funds
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Cash and cash equivalents				4,800,000		4,800,000		$ 4,800,000
Testing Services
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Deferred revenue				$ 3,500,000		$ 3,500,000
Accounts Receivable | Customer Concentration Risk
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Concentration risk, percentage						17.00%		18.00%
Accounts Receivable | Diagnostic Tests | Customer Concentration Risk
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Concentration risk, percentage						61.00%	58.00%
Diagnostic Test Revenue | Customer Concentration Risk
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Concentration risk, percentage				63.00%	57.00%	61.00%	58.00%
Customer One | Accounts Receivable | Customer Concentration Risk
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Concentration risk, percentage						10.00%		44.00%
Customer One | Accounts Receivable | Diagnostic Tests | Customer Concentration Risk
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Concentration risk, percentage						35.00%		0.00%
Two Service Customers | Service Revenue | Customer Concentration Risk
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Concentration risk, percentage						53.00%	85.00%
Health Care Provider | Diagnostic Test Revenue | Customer Concentration Risk
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Concentration risk, percentage				62.00%		42.00%
IPO
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Reverse stock split, description						0.1684664-for-1
IPO | Subsequent Event
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Net proceeds	$ 63,000,000.0		$ 63,000,000.0
Reverse stock split ratio		0.1684664
Shares of common stock issued and sold | shares	4,000,000
Common stock price per share | $ / shares	$ 18.00
Convertible preferred stock and convertible notes payable converted into shares of common stock | shares	21,939,025