Antigen tests are typically immunoassays that detect the presence of a specific viral antigen. For the SARS-CoV-2 virus, antigen tests can be used to indicate current COVID-19 infection. The tests are performed on nasopharyngeal or nasal swab specimens placed directly into the assay’s extraction buffer or reagent. Antigen tests generally have similar specificity but are less sensitive than most molecular tests (NAATs, RT-PCR). Antigen tests are relatively inexpensive and most can be performed at the point of care (POC) with results available in minutes. This makes them amendable to be used in screening programs to more quickly identify those who are likely to be contagious. Because of the decreased sensitivity of antigen tests, it may be necessary to confirm some antigen test results (e.g., a negative test in persons with symptoms or a positive test in persons without symptoms) with a molecular-based test (NAAT).
