Connell F A, Koepsell T D
Am J Epidemiol. 1985 May;121(5):744-53. doi: 10.1093/aje/121.5.744.
The authors propose several measures for quantifying the change in the clinical estimate of a patient's chances of having a disease that occurs as a result of diagnostic testing. Under most circumstances, the gain in clinical certainty from a positive test result is more affected by the specificity (T) of the test, while the gain from a negative test result is more affected by sensitivity (S). The prevalence of the disease in the tested population is also an important determinant of the magnitude of gain in certainty. Measures of the expected gain in certainty can be calculated by weighting the gains from a positive or negative result by the likelihood of the respective test outcome. Indices of expected gain depend directly on the quantity S + T, implying that sensitivity and specificity have equal importance in determining expected gain. When S + T = 1, the test provides no information; when S + T is greatest, the expected gain is maximized. Expected gain is also related to the receiver operating characteristic curve for a diagnostic test: the point on the receiver operating characteristic curve at which S + T is greatest corresponds to the point at which the distance from the major diagonal is greatest at which the slope of the receiver operating characteristic curve equals 1.
作者提出了几种用于量化因诊断测试而导致的患者患某种疾病可能性的临床估计变化的方法。在大多数情况下，阳性测试结果带来的临床确定性增加更多地受测试的特异性（T）影响，而阴性测试结果带来的增加则更多地受敏感性（S）影响。所测试人群中疾病的患病率也是确定性增加幅度的一个重要决定因素。确定性预期增加的度量可以通过将阳性或阴性结果的增加按各自测试结果的可能性进行加权来计算。预期增加指数直接取决于S + T的值，这意味着敏感性和特异性在确定预期增加方面具有同等重要性。当S + T = 1时，测试不提供任何信息；当S + T最大时，预期增加最大。预期增加也与诊断测试的接收者操作特征曲线相关：接收者操作特征曲线上S + T最大的点对应于与主对角线距离最大且接收者操作特征曲线斜率等于1的点。
