Rapid antigen tests are commonly used in the diagnosis of respiratory pathogens including influenza viruses.  Rapid antigen tests perform best when the person is tested in the early stages of infection with SARS-CoV-2 when viral load is generally highest.  The FDA cites rapid antigen tests can be used for screening testing in settings in which repeat testing could quickly identify persons with SARS-CoV-2 infection to inform infection prevention and control measures, thus preventing transmission.  Further, in such setting, immediate results with antigen tests can be more valuable even though they may have lower sensitivity than PCR tests, especially when rapid turnaround time is required.

The table below highlights some key points of differentiation between PCR and antigen tests.

Summary of Some Differences between RT-PCR Tests and Antigen Tests

RT-PCR Tests Antigen Tests
Intended Use Detect Current Infection Detect Current Infection
Analyte Detected Viral RNA Viral Antigens
Specimen Type(s) Nasal Swab, Sputum, Saliva Nasal Swab
Sensitivity High Moderate
Specificity High High
Test Complexity Varies Relatively Easy to Use
Authorized for Use at the Point-of-Care Most devices are not, some devices are Yes
Turnaround Time Ranges from 15 minutes to > 2 days Approximately 15 Minutes
Cost/Test Moderate Low

Source:  Interim Guidance for Rapid Antigen Testing for SARS-CoV2, September 4, 2020