In recent days readers of KMC Clinic health articles have heard a new term, namely Rapid Antigen or Swab Antigen. Basically, this antigen swab is not a test that can be used as a standard for diagnosing Covid-19, but it is very helpful because it is easy to do anywhere and anytime with a much better test accuracy than rapid antibodies. The swab antigen is a rapid, lateral flow antigen test, a type of test that runs a liquid sample along a surface with reactive molecules. The test detects fragments of proteins of the SARS-CoV-2 virus from a nasal swab sample from any individual 2 years of age or older.
According to FDA authorities, swab antigen is similar to other antigen tests, a small percentage of positive and negative results from this test may be false. Therefore, for patients without symptoms, positive results should be treated as presumptively positive until confirmed by another test as soon as possible. This is especially true if there are fewer infections in a particular community, as false-positive results can be more common when antigen tests are used in populations where there are little COVID-19 (low prevalence).
The FDA reminds patients that all tests can experience false-negative and false-positive results. Individuals with positive results should self-isolate and seek additional care from their health care provider. Individuals who test negative and experience COVID-like symptoms should follow up with their health care provider as negative results do not preclude an individual from SARS-CoV-2 infection.
This is the difference between the PCR and Antigen Swab Test: