There are two major categories of COVID-19 tests being offered at this time (AUGUST 2020): diagnostic tests and antibody tests.
Diagnostic tests allow for identification of active infection and there are currently two different diagnostic tests available.
Nucleic acid amplification testing most commonly with a reverse-transcription polymerase chain reaction (RT-PCR) assay can be used to test directly for SARS-CoV-2 viral RNA (COVID-19) viral RNA.
Antigen testing is used to detect specific proteins located on the viral surface. Both tests require a nasal swab.
The advantage of RT-PCR testing is that it is highly accurate, whereas a negative antigen test may require confirmation with additional PCR testing to ensure that the virus is not present.
Antibody testing is different in that it requires a small blood sample to detect specific antibodies made by the immune system in response to the virus. Antibody testing does not screen directly for the virus itself, but the immune system’s response to the virus. It can take several days or weeks for the immune system to amount a response to a virus, making this test better utilized for the purpose of diagnosing previous infection.