antigentests

Antigen tests, also known as rapid antigen tests, are diagnostic tests that detect specific protein antigens from a pathogen, most commonly a virus. They are designed for quick results and are frequently used at the point of care or at home. They differ from molecular tests that detect genetic material.

Most antigen tests rely on an immunoassay format, often a lateral flow assay. A sample collected from the nose or throat is exposed to antibodies on a test strip. If the target antigen is present, a color change or line appears, indicating a positive result. Results are typically available within 15 to 30 minutes.

Common specimen types include nasal swabs, nasopharyngeal swabs, anterior nasal swabs, and in some tests, saliva. Sample collection technique can affect test performance, with improper collection reducing sensitivity.

Performance characteristics generally show high specificity, meaning false positives are uncommon. Sensitivity, however, can vary and is usually lower than that of molecular tests. Sensitivity tends to be higher when viral load is greatest, such as near symptom onset, and lower in asymptomatic individuals or later in infection. Because of limited sensitivity, negative results, especially in symptomatic individuals or known exposures, may require confirmatory molecular testing.

Uses and limitations: antigen tests are useful for rapid screening in homes, schools, workplaces, and clinical settings. They provide fast results, are generally inexpensive, and simple to administer, but negative results do not definitively rule out infection. Regulatory approvals and instructions vary by country. Proper storage, handling, and adherence to the manufacturer’s instructions are essential for accuracy.