Are COVID-19 tests accurate? Which COVID-19 tests are more accurate? When is the COVID-19 confirmation test suggested?
There are three types of tests for Covid – PCR-based test that detects viral RNA, Rapid Antigen test that detects viral protein, and the serological test that detects antibodies against SARS-CoV 2 virus proteins. PCR-based tests are highly sensitive, i.e., the probability of missing a positive case is low and specific, i.e., the probability of the test being wrong is low, and hence, is used as the definitive test for Covid. Rapid Antigen Tests (RAT) have low sensitivity, i.e., a negative test does not rule out Covid, while being specific. Serological tests become positive a week or two after the infection or vaccination. Positive IgM antibody is suggestive of recent infection or vaccination, while IgG antibody is suggestive of prior infection or vaccination. Each of the above tests has to be always interpreted in the context of clinical presentation. In summary, all approved Covid tests are reasonably accurate; of these PCR-based tests are the most accurate in diagnosis; and Covid confirmation test is suggested in every suspected patient (clinical presentation of influenza-like illness or direct exposure to a positive case)