ABSTRACT
Diagnostic tests are applied at the herd level to determine the incidence and/or prevalence of disease within the herd, to identify the cause of a disease process, and sometimes to select those animals that should be culled. A diagnostic test does not have to be laboratory based, but it should provide information upon which decisions can be made. A distinction must be made between diagnostic and screening test scenarios. Diagnostic testing begins with diseased individuals, whereas screening begins with presumably healthy individuals. Accuracy is often used to express the overall performance of a diagnostic test. Postmortem examination is used more frequently as a diagnostic tool in veterinary medicine than in human medicine. The predictive value of diagnostic results can be improved by selecting more sensitive or specific tests. The relationship among the above measures of diagnostic test performance can be appreciated from the following report on the development of an enzyme-linked immunosorbent assay for dermatophytosis in cats.
