GID Z p FDR AUC AUCc ICC 191  3.797 0.00015 0.0181  0.8704 0.8704 93.3 264 -3.497 0.00047 0.0353  0.8457 0.9167 89.1 133 -3.149 0.00164 0.0584  0.8148 0.9660 88.7 136 -3.058 0.00223 0.0602  0.8117 0.9722 82.2 135 -2.959 0.00309 0.0756  0.7932 0.9784 93.3 384 -2.927 0.00342 0.1490  0.7901 0.9815 94.5 134 -2.897 0.00377 0.0668  0.7901 1.0000 81.7  93 -2.864 0.00418 0.0629  0.7840 1.0000 91.5 379 -2.864 0.00419 0.1186  0.7840 1.0000 94.5 137 -2.792 0.00524 0.0807 0.7932 1.0000 88.9

Table 2: Wilcoxon-Mann-Whitney two-sample rank sum test applied to screened, quantile-normalized median summarized data from the Nickel Exposure Study. The samples contain 18 subjects with high (≥ 9.98 µg/L) and 18 subjects with low (≤4.44 µg/L) level of urinary Nickel. The meaning of columns are as follows: GID – glycan identification number, Z – z-statistic, p – p-value of the test, FDR – false discovery rate, AUC – area under the ROC curve, AUCC – cumulative AUC value obtained by combining the above glycans through multivariate logistic regression, ICC – corresponding Intra-class Correlation Coefficient computed for raw data. The sign of the z-statistic indicates downregulation (negative sign) or upregulation (positive sign) of normalized signals. The low values of FDR, at least for top three glycans, imply a good confidence in the results. The glycans in the table are sorted by ascending order of the p-value. The sixth column suggests that combining several glycans can considerably increase the AUC value. For example, combining three top glycans: GID = 191, 264, 133, gives AUCC = 0.966. Figure 13 shows a solid statistical significance for this AUC value.