Department of Clinical Psychology, Faculty of Psychology and Education, Vrije Universiteit, Van der Boechorststraat 1, 1081 BT Amsterdam, the Netherlands.
BMC Med Res Methodol. 2010 Sep 30;10:89. doi: 10.1186/1471-2288-10-89.
The Youden index, the sum of sensitivity and specificity minus one, is an index used for setting optimal thresholds on medical tests.
When using this index, one implicitly uses decision theory with a ratio of misclassification costs which is equal to one minus the prevalence proportion of the disease. It is doubtful whether this cost ratio truly represents the decision maker's preferences. Moreover, in populations with a different prevalence, a selected threshold is optimal with reference to a different cost ratio.
The Youden index is not a truly optimal decision rule for setting thresholds because its cost ratio varies with prevalence. Researchers should look into their cost ratio and employ it in a decision theoretic framework to obtain genuinely optimal thresholds.
约登指数是一种用于确定医学检测最佳阈值的指标，它等于敏感度和特异度之和减一。
使用该指数时，人们会隐含地使用决策理论，并使用误分类成本的比值，该比值等于疾病流行率的倒数。这种成本比值是否真的代表决策者的偏好是值得怀疑的。此外，在流行率不同的人群中，选择的阈值与不同的成本比值相关，是最优的。
由于约登指数的成本比值随流行率而变化，因此它不是设置阈值的真正最优决策规则。研究人员应该研究其成本比值，并在决策理论框架内使用它，以获得真正最优的阈值。
