Accommodating covariates in receiver operating characteristic analysis
ABSTRACT: Although alpha-fetoprotein (AFP) is the most widely used biomarker in hepatocellular carcinoma (HCC) surveillance, disease activity may also increase AFP levels in chronic hepatitis B (CHB).
Since nucleos(t)ide analog (NA) therapy may reduce not only HBV viral loads and transaminase levels but also the falsely elevated AFP levels in CHB, we tried to determine whether exposure to NA therapy influences AFP performance and whether selective application can optimize the performance of AFP testing in CHB during HCC surveillance.
We identified 49 women with invasive squamous cell cancer of the cervix and 22 women with normal cytology specimens.
Classification accuracy is the ability of a marker or diagnostic test to discriminate between two groups of individuals, cases and controls, and is commonly summarized using the receiver operating characteristic (ROC) curve.
In studies of classification accuracy, there are often covariates that should be incorporated into the ROC analysis.
For factors that affect marker observations among controls, we present a method for covariate adjustment.
For factors that affect discrimination (ie the ROC curve), we describe methods for mod- elling the ROC curve as a function of covariates.