Absolute numbers of true positive (TP), true negative (TN), false positive (FP) and false negative (FN) test results were extracted for each included study. Where zero values occurred, a continuity correction of 0.5 was added to all values for that study, to allow calculation of sensitivity and specificity. Estimates of sensitivity, specificity, positive and negative predictive values, and positive and negative likelihood ratios (LRs), with 95% confidence intervals (CIs), were calculated for each study.
Data were independently extracted by two reviewers and cross-checked. Disagreements were resolved by consensus, or consultation with a third reviewer.