Antigen tests are immunoassays that detect the presence of a specific viral antigen, which suggests current viral infection. Antigen tests are commonly used in the diagnosis of respiratory pathogens, including influenza viruses and respiratory syncytial virus (RSV). The U.S. Food and Drug Administration (FDA) has granted emergency use authorization (EUA) for antigen tests that can identify SARS-CoV-2. See FDA’s list of In Vitro Diagnostics EUAs.
SARS-CoV-2 antigen tests are currently authorized for nasopharyngeal swab and nasal swab specimens. The currently authorized antigen tests include point-of-care (POC), laboratory-based, and self-tests available without a prescription. Certain tests have age limitations; refer to FDA’s website for more details.
Antigen tests produce results quickly (within minutes), and most can be used at the POC or at home. Most self-tests, or at-home tests, are antigen tests. Antigen tests are better at detecting a SARS-CoV-2 infection when someone has COVID-19 symptoms compared to if they do not. Antigen tests for SARS-CoV-2 are generally less sensitive than real-time reverse transcription polymerase chain reaction (RT-PCR) and other nucleic acid amplification tests (NAATs), which detect and amplify the presence of viral nucleic acid. For this reason, in situations where test sensitivity is of paramount importance, NAAT tests are preferred. For additional comparison between NAAT and antigen tests, please see the Summary Table of NAAT and Antigen Test Differences.
Accurate identification of infection and clinical management of COVID-19 requires performing the test properly and correctly interpreting the results. Patients who test positive should follow CDC isolation guidance for next steps. All initial negative antigen test results should be confirmed with a NAAT or repeated with additional antigen tests following FDA’s recommendations on repeat testing.
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