title: A model-free estimation for the covariate-adjusted Youden index and its associated cut-point.
abstract: In medical research, continuous markers are widely employed in diagnostic tests to distinguish diseased and non-diseased subjects. The accuracy of such diagnostic tests is commonly assessed using the receiver operating characteristic (ROC) curve. To summarize an ROC curve and determine its optimal cut-point, the Youden index is popularly used. In literature, the estimation of the Youden index has been widely studied via various statistical modeling strategies on the conditional density. This paper proposes a new model-free estimation method, which directly estimates the covariate-adjusted cut-point without estimating the conditional density. Consequently, covariate-adjusted Youden index can be estimated based on the estimated cut-point. The proposed method formulates the estimation problem in a large margin classification framework, which allows flexible modeling of the covariate-adjusted Youden index through kernel machines. The advantage of the proposed method is demonstrated in a variety of simulated experiments as well as a real application to Pima Indians diabetes study.
authors.affiliation: Amgen Inc.; Department of Mathematics, Statistics, and Computer Science, University of Illinois at Chicago, Chicago, IL, U.S.A.
authors.forename: Tu
authors.initials: T
authors.lastname: Xu
authors.forename: Junhui
authors.initials: J
authors.lastname: Wang
authors.forename: Yixin
authors.initials: Y
authors.lastname: Fang
mesh_terms: D015415:Biomarkers / Q000032:analysis*; D001786:Blood Glucose / Q000032:analysis; D003198:Computer Simulation; D003627:Data Interpretation, Statistical; D003920:Diabetes Mellitus / Q000097:blood; D003955:Diagnostic Tests, Routine / Q000379:methods*; D005260:Female; D005951:Glucose Tolerance Test; D006801:Humans; D007198:Indians, North American; D008297:Male; D008875:Middle Aged
chemical_list: D015415:Biomarkers; D001786:Blood Glucose
keywords: Youden index; diagnostic accuracy; margin; receiver operating characteristic curve; reproducing kernel Hilbert space