To assess the performance of the peptide biomarker panel in the classification of "unknown" samples, we carried out an experimental bootstrapping approach. Instead of in silico bootstrapping simulation, samples belonging to different visits of the same patient and even the same samples were assayed, i.e., "bootstrapped" experimentally, for testing. For the bootstrapping testing, a total of 52 SJIA samples (demographics shown in Tables 4 and 5) were analyzed by the antibody array where 41 samples were from 19 patients at the time of SJIA flare, and 11 samples were from eight patients at the time of SJIA quiescence. Figure 4b plots the linear discriminant probabilities of the peptide biomarker panel for the training (left) and bootstrapping data (right); in both cases, samples had good separation between the highest and next highest probability for the classification.