Decision theory for clinicians: uses and misuses of clinical tests

There is no clear cutoff between normal and abnormal for most clinical measurements and laboratory tests. Since normal limits for many laboratory tests are established by statistical methods, it is imperative that the clinician base his interpretation of the laboratory results on the clinical situation. In addition, a clinician should realize that the prevalence of disease is affected by the setting in which he practices, and the manner in which he uses a clinical test can affect the predictive value of the test used.