STRATIFICATION IN NONPARAMETRIC ROC STUDIES

In many clinical experiments it is clear that external factors can aff ect the performance of diagnostic tests as these factors influence the distributions of separator variables. The authors investigate how str atification of cases and/or controls can be used in nonparametric rece iver operating characteristic (ROC) studies, and develop statistical m ethods using stratification. The method can be used to simultaneously assess the ability of a diagnostic marker against several types of con trols or cases. This allows a new method for the assessment of diagnos tic tests.