Semiparametric receiver operating characteristic analysis to evaluate biomarkers for disease

The receiver operating characteristic (ROC) curve is a popular method for characterizing the accuracy of diagnostic tests when test results are not binary. Various methodologies for estimating and comparing ROC curves have been developed. One approach, due to Pepe, uses a parametric, regression model ROCx(u) = g(h(0)(u) +0(0)'x) with the baseline function h(0)(u) specified up to a finite-dimensional parameter. In this article we extend the regression models by allowing arbitrary nonparametric baseline functions. We also provide asymptotic distribution theory and procedures for making statistical inference. We illustrate our approach with dataset from a prostate cancer biomarker study. Simulation studies suggest that the extra flexibility inherent in the semiparametric method is gained with little loss in statistical efficiency.