COVID-19 Testing: PCR or Rapid Antigen Test
|PCR||Rapid Antigen Test|
|What it tests for||Molecular material from the virus is magnified through polymerase chain reaction (PCR) to detect very small amounts of RNA||Proteins from the surface of the virus, not magnified|
|Type of sample||Nasal swab (at Yale) or saliva||Nasal swab|
|Where it is performed||In a lab||At home kit or in a clinical setting (called point of care testing)|
|Speed||Typically takes about 24 hours to receive a result, but depends on the lab on other factors||About 15 minutes|
Very accurate, considered the “gold standard.” Can detect very small amounts of virus early in infection. May also detect left over viral material later in infection when the person is no longer contagious.
|Less ability to detect small amounts of virus. Negative results may be false negatives (showing a negative result when infection is actually present) early in disease when the amount of circulating virus is low. Positive tests are highly reliable.|
|What a positive result tells you||Evidence of active viral infection or, late in disease (14-90 days out), evidence of past infection.||
Evidence of active viral infection with sufficient levels of virus to be infectious to others. No need to confirm with another test in most cases.
|What a negative result tells you||
No evidence of infection at the time of the test.
|Does not rule out infection. It is unlikely that you have enough circulating virus to be infectious at the time of a negative test. Should be repeated in 24-48 hours in settings of known exposure or if symptoms present.|
|When to use it||