A blood test to detect the presence of antibodies against a microorganism.
Deeper dive
Antibodies are proteins that the body creates when it detects a foreign presence, such as bacteria or virus.
A serologic test can determine whether a person has been exposed to a particular microorganism, and the potential that they are immune to a disease.
With COVID-19, some people have had a serologic test to determine their antibody levels for SARS-CoV-2, the virus that causes COVID-19 disease. Those with high levels of antibodies in their blood indicate that a person may have been exposed to or recovered from COVID-19, or their body has responded to the COVID-19 vaccine. But the Food and Drug Administration says antibodies in the blood do not necessarily mean someone is protected from COVID-19 infection and therefore serologic tests are not recommended for use by the general public.