Figure 2

Cross-validation performance of univariate models. The predictive value of each variable was evaluated based upon 10,000 cross-validation trials. In each trial, a univariate Cox PH model was fit using a randomly chosen training dataset, and model performance was evaluated by applying the fitted model to subjects within a randomly chosen testing dataset. The predictive value of each variable was measured according to the average concordance index (C) among simulation trials (see Methods). The concordance index is an average of time-specific area under the curve statistics (i.e., AUC(t)), which were calculated for t = 1, ..., 19 years of follow-up time (see Methods). Part (A) shows the distribution of mean concordance estimates among all 377 predictor variables. In part (B), for each variable, the average value of AUC(19) among simulation trials is plotted against the average value of AUC(1).