Introduction Fluorescent antibody testing can be divided into direct fluorescent antibody test (DFA) use for antigen localization and detection via a fluorescently labeled antibody that binds to the antigen of interest examples used to help in diagnosing varicella zoster virus (VZV) infection Legionella infection herpes simplex virus (HSV) infection indirect fluorescent antibody test (IFA) use for pathogen-specific antibody detection via a fluorescently labeled anti-antibody mixed with the patient's serum that contains the produced antibody and the laboratory-generated infected tissue sample examples used to detect the presence of anti-nuclear antibodies anti-dsDNA antibodies anti-glomerular basement membrane antibodies