TEST CHARACTERISTICS AND DECISION RULES
Section snippets
Sensitivity and Specificity
Physicians traditionally think of two characteristics in assessing the usefulness of a diagnostic test—sensitivity and specificity. These characteristics are frequently misunderstood and improperly used. The sensitivity of a test is determined by the proportion of persons with a disease who have a positive test; it is also referred to as the "true positive rate." Specificity, on the other hand, is the proportion of persons free of disease who have a negative test; this is also referred to as
CLINICAL DECISION RULES
Accurate estimates of the likelihood of disease, prognosis, and response to treatment are central to clinical practice. More accurate estimates help physicians to make better-informed decisions. Knowing that a patient is at high risk for the development of endometrial cancer could lead a physician to consider a more aggressive case-finding approach for the disease than is ordinarily recommended, such as an annual endometrial biopsy. Patients at low risk can be reassured; they are spared an
SUMMARY
We have demonstrated using several examples how different test characteristics can be used to assist clinicians in making better decisions for their patients. These probabilistic models may seem confusing and difficult to implement. Some general rules may help, such as SnNout and SpPin. Clinicians should know the test characteristics and decision rules for the acute problems they may face. For chronic conditions, advanced planning may be helpful. Electronic medical record systems may be able to
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Address reprint requests to Henry C. Barry, MD, MS Department of Family Practice B–100 Clinical Center East Lansing, MI 48824–1313