Immunologic Tests for Infectious Disease By Maria T Vazquez-Pertejo, MD, FACP, Wellington Regional Medical Center Reviewed / Revised Oct 2022 View Patient Education Immunologic tests use one of the following: Antigen to detect antibodies to a pathogen in the patient's specimen Antibody to detect an antigen of the pathogen in the patient's specimen Specimen handling varies, but if testing is to be delayed, the specimen should typically be refrigerated or frozen to prevent overgrowth of bacterial contaminants.