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
Accuracy	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. Faculty, staff, and students who test positive on a PCR test outside of the university’s Color program, should report it to the university.	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. Faculty, staff, and students should report a positive rapid antigen test to the university. Yale Health dependents should contact their health care provider.
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. Perform a PCR test if available. If a PCR test is not available, repeat the rapid antigen test in 48 hours, especially in settings of known exposure or if symptoms present.
When to use it	Preferred for most accurate diagnosis. For symptomatic testing when the turnaround time is good. For screening when you do not have symptoms. If you were exposed to someone who tested positive for COVID-19 but you do not have symptoms, take 2 tests, one at notification and one 5 days later.	For symptomatic testing when a rapid answer is needed (trust a positive, repeat a negative as noted above). For testing immediately prior to an indoor event or travel if you do not have symptoms (a single negative test cannot fully rule out infection, but it is unlikely you are infectious). If you were exposed to someone who tested positive for COVID-19 but you do not have symptoms, take 2 tests, one at notification and one 5 days later.