| Figure 1. Readout of Xpert® MTB/RIF assay for a TB positive, rifampicin-susceptible specimen. Courtesy: Karin Weyer, the Global TB Programme, WHO |
| Figure 2. Flow diagram of studies in the review |
| Figure 3. Risk of bias and applicability concerns graph: review authors' judgements about each domain presented as percentages across the 36 included study centres (27 studies). The reference standard domain pertains to TB as the target condition. See text for the reference standard relating to rifampicin resistance. |
| Figure 4. Risk of bias and applicability concerns summary: review authors' judgements about each domain for each included study centre. |
| Figure 5. Forest plots of Xpert MTB/RIF sensitivity and specificity for TB detection, Xpert MTB/RIF used as an initial test replacing smear microscopy. The individual studies are ordered by decreasing sensitivity. TP = True Positive; FP = False Positive; FN = False Negative; TN = True Negative. Between brackets are the 95% CI of sensitivity and specificity. The figure shows the estimated sensitivity and specificity of the study (blue square) and its 95% CI (black horizontal line). Xpert MTB/RIF specificity could not be estimated in one study. |
| Figure 6. Summary plots of Xpert MTB/RIF sensitivity and specificity for TB detection, Xpert MTB/RIF used as an initial test replacing smear microscopy. Each individual study is represented by an empty square. The size of the square is proportional to the sample size of the study such that larger studies are represented by larger squares. The filled circle is the median pooled estimate for sensitivity and specificity. The solid curves represent the 95% credible region around the summary estimate; the dashed curves represent the 95% prediction region. |
| Figure 7. Study results of smear microscopy (green circle) versus Xpert MTB/RIF (red circle) plotted in ROC space. The specificity of smear was assumed to be 100%. |
| Figure 8. Forest plots of Xpert MTB/RIF for TB detection in studies reporting data for smear-negative patients. We also used these data as a proxy for the accuracy of Xpert MTB/RIF used as an add-on test following a negative smear microscopy result. TP = True Positive; FP = False Positive; FN = False Negative; TN = True Negative. Between brackets the 95% CI of sensitivity and specificity. The figure shows the estimated sensitivity and specificity of the study (blue square) and its 95% CI (black horizontal line). |
| Figure 9. Summary plots of Xpert MTB/RIF sensitivity and specificity for TB detection, Xpert MTB/RIF used as an add-on test following a negative smear microscopy result. Each individual study is represented by an empty square. The size of the square is proportional to the sample size of the study such that larger studies are represented by larger squares. The filled circle is the median pooled estimate for sensitivity and specificity. The solid curve represents the 95% credible region around the summary estimate; the dashed curves represent the 95% prediction region. |
| Figure 10. Forest plot of Xpert MTB/RIF sensitivity for TB detection in studies reporting data for smear-positive patients. The squares represent the sensitivity and specificity of one study, the black line its CI. TP = true positive; FP = false positive; FN = false negative; TN = true negative. Xpert MTB/RIF specificity could not be estimated in these studies. |
| Figure 11. Forest plots of Xpert MTB/RIF sensitivity and specificity for TB detection in HIV-positive and HIV-negative subgroups. The squares represent the sensitivity and specificity of one study and the black line represent its CI. TP = true positive; FP = false positive; FN = false negative; TN = true negative. |
| Figure 12. Forest plots of Xpert MTB/RIF sensitivity and specificity for detection of rifampicin resistance, Xpert used as an initial test replacing conventional DST as the initial test. The individual studies are ordered by decreasing sensitivity and decreasing number of true positives. The squares represent the sensitivity and specificity of one study, the black line its CI. TP = true positive; FP = false positive; FN = false negative; TN = true negative. |
| Figure 13. Bayesian bivariate hierarchical model, likelihood. |
| Figure 14. Bayesian bivariate hierarchical model, prior distributions. |
| Test 1. TB detection, all studies. |
| Test 2. Add on. |
| Test 3. Smear positive. |
| Test 4. Smear negative. |
| Test 5. HIV positive. |
| Test 6. HIV negative. |
| Test 7. TB detection, condition of specimen. |
| Test 8. TB detection, specimen preparation. |
| Test 9. Proportion TB cases. |
| Test 10. Income status. |
| Test 11. RIF resistance detect. |
| Test 12. Xpert version. |
| Test 13. Proportion RIF resistance. |