SARS-CoV-2
Test Types
Viral tests, including Nucleic Acid Amplification Tests (NAATs, such as Reverse Transcription – Polymerase Chain Reaction), antigen tests and other tests (such as breath tests) are used as diagnostic tests to detect current infection with SARS-CoV-2 and to inform an individual’s medical care. Viral tests can also be used as screening tests to reduce the transmission of SARS-CoV-2 by identifying infected persons who need to isolate from others.
Polymerase Chain Reaction (PCR)
PCR tests are highly sensitive and highly specific tests that detect one or more viral ribonucleic acid (RNA) genes and indicate a current infection. Viral RNA may stay in a person’s body for up to 90 days after they test positive. Therefore, PCR should not be used to test someone who has tested positive in the last 90 days. Most PCR need to be performed in a laboratory, however some are performed at the point-of-care. Most NAATs produce qualitative (positive/negative) results.
Antigen tests
Antigen or otherwise called "rapids" are immunoassays that detect the presence of a specific viral antigen. Antigen tests generally have similar specificity, but are less sensitive than most NAATs. Most are less expensive than NAATs and can provide results in minutes. There are antigen tests available for at-home testing (self-testing), at the point of care, or in a laboratory. As noted in the labeling for authorized over-the- counter antigen tests: Negative results should be treated as presumptive (meaning that they are preliminary results). Negative results do not rule out SARS-CoV-2 infection and should not be used as the sole basis for treatment or patient management decisions, including infection control decisions. Please see FDA guidance on the use of at-home or POC COVID-19 antigen tests.