Explanation for calculation of theoretical sensitivity and specificity.

<p>The theoretical sensitivity is the likelihood of sensitivity of the clinical rule after combining <i>n</i> tests, thus its values is depend on the individual sensitivity of each test. For example, a clinical rule combining two tests with sensitivities at 90% and 80%, respectively, the likelihood of the combined sensitivity (of the clinical rule of two tests) is calculated as 1–(1–0.90)×(1–0.80) = 0.98 or 98%. Therefore, combination of several tests will enhance the rule's sensitivity. In contrast, a clinical rule combining two tests with specificities at 80% and 70%, the likelihood of the combined specificity (of the clinical rule of two tests) will be decreased as the follow calculation: 0.80×0.70 = 0.56 or 56%.