Sensitivity, specificity, performance index, and positive and negative predictive values of the test calculated for different cutoff valuesa.

aThe analysis was performed using 138 sera as positive-controls and 350 sera as negative-controls.bSe, sensitivity (TP/TP+FN)×100; Sp, specificity (TN/TN+FP)×100. Values in parentheses indicate the 95% confidence interval. TP, true positives; TN, true negatives; FP, false positives; FN, false negatives.cPI, performance index calculated as the sum of the sensitivity and specificity values.dPPV, positive predictive value (TP/TP+FP)×100; NPV, negative predictive value (TN/TN+FN)×100.eMaximum values for Se, Sp, PI, PPV and NPV are indicated in bold.