ABSTRACT
Serology is the study of antigen-antibody binding in vitro and it has major significance in clinical medicine. Most practising veterinarians will employ diagnostic serological testing at least once every day. One of the most common applications of serology is in the diagnosis of infectious disease. Serological tests may be used to detect minute quantities of microbial antigen in a sample or, more commonly, look for evidence of antibody specific for that organism as evidence that the animal has been exposed to that agent. More refined serological tests may be used to quantify the amount of antibody present, and by collecting paired samples from a patient (e.g. two weeks apart) one can determine whether the amount of antibody might be increasing (as in an active progressing infection) or decreasing (as in recovery). Some serological tests are designed to detect either IgG or IgM antibody and the relative proportions of these may indicate the stage of the infection. Serological
tests are most commonly performed on blood samples or the serum fraction of blood, but they have equal applicability to a range of other body fluids.
