THE DIAGNOSTIC SPECIFICITY AND SENSITIVIT Y AND THE IMPORTANCE OF PREVALENCE

In this paper the terms <<diagnostic specificity, sensitivity and effi ciency>> are explained using the example of feline immunodeficiency vi rus (FIV). Clinical conditions are discussed which require tests with high sensitivity and/or specificity. In addition it is shown that the prevalence of a disease is an important factor for the predictive valu e of a test result. For instance, tests with good specificity will lea d to a high proportion of false negative values if the prevalence of t he disease detected by the test is low. In order to improve the predic tive value of a positive tet result, the clinician must try to assign a patient to a population of individuals in which the prevalence of th e suspected disease is elevated. This can be done by carefully evaluat ing the history and the clinical signs.