What is serology or a serology test?
Serology refers to the study of blood serum, and the vast majority of serology testing is done to detect antibodies.
Other body fluids, like saliva, can be tested too, but that's because they contain trace elements of blood, which is what's actually being tested.
Serology tests can also determine blood type when donating blood or receiving a transfusion. They can be used to measure the levels of pharmaceuticals present in the bloodstream, during a drug trial, for example. But most of the time, when experts use the phrase "serology" or "serology testing," they're talking about antibody tests.