Organization and Description of Business - Additional Information (Details) $ / shares in Units, $ in Thousands			12 Months Ended
	Oct. 27, 2020 USD ($) $ / shares shares	Oct. 19, 2020	Dec. 31, 2020 USD ($) Test $ / shares shares	Oct. 31, 2020 $ / shares shares	Dec. 31, 2019 $ / shares shares
Organization And Description Of Business [Line Items]
Number of blood based lung cancer test | Test			4
Number of commercial blood-based test | Test			2
Number of SARS-CoV-2 test | Test			2
Reverse stock split, description			0.1684664-for-1
Reverse stock split ratio		0.1684664
Common stock, shares authorized			200,000,000	200,000,000	190,000,000
Common stock, par value | $ / shares			$ 0.001	$ 0.001	$ 0.001
Preferred stock, shares authorized			5,000,000	5,000,000	0
Preferred stock, par value | $ / shares			$ 0.001	$ 0.001	$ 0.001
Proceeds from initial public offering | $			$ 72,000
Warrants to purchase shares of common stock			103,326
Initial Public Offering
Organization And Description Of Business [Line Items]
Shares of common stock issued and sold	4,000,000
Common stock price per share | $ / shares	$ 18.00
Proceeds from initial public offering | $	$ 63,800
Convertible preferred stock and convertible notes payable converted into shares of common stock	21,939,025
Warrants to purchase shares of common stock	103,326		103,326