serological test, also called serology test or antibody test, any of several laboratory procedures carried out on a sample of blood serum (the clear liquid that separates from the blood when it is allowed to clot) for the purpose of detecting antibodies or antibody-like substances that appear specifically in association with certain diseases. There are different types of serological tests—for example, flocculation tests, neutralization tests, hemagglutinin-inhibition tests, enzyme-linked immunosorbent assays (ELISAs), and chemiluminescence immunoassays.