Table 4.
The area under the ROC curve and cut-off points of conventional and molecular tests compared to Xpert MTB/RIF Ultra.
| Variable | AUC/ROC (CI 95%) | Sensibility | Especificity | LHR+ | LHR− | VPP | VPN | Prevalence |
|---|---|---|---|---|---|---|---|---|
| All samples | ||||||||
| Smear | 0.685 (0.592–0.777) | 37.04 | 100.0 | – | 0.629 | 100.0 | 85.30 | 21.0 |
| Mycobacteria culture | 0.697 (0.628–0.767) | 39.58 | 100.0 | – | 0.604 | 100.0 | 81.40 | 27.0 |
| Cobas MTB | 0.954 (0.914–0.994) | 91.67 | 99.21 | 116.4 | 0.084 | 97.80 | 96.90 | 27.0 |
| Logix Smart MTB | 0.896 (0.835–0.957) | 80.95 | 98.31 | 47.76 | 0.193 | 94.40 | 93.50 | 26.0 |
| Pulmonary samples | ||||||||
| Smear | 0.700 (0.602–0.798) | 40.00 | 100.0 | – | 0.600 | 100.0 | 81.30 | 28.0 |
| Mycobacteria culture | 0.726 (0.650–0.802) | 45.24 | 100.0 | – | 0.547 | 100.0 | 78.50 | 33.0 |
| Cobas MTB | 0.964 (0.924–0.999) | 92.86 | 100.0 | – | 0.071 | 100.0 | 96.60 | 33.0 |
| Logix Smart MTB | 0.891 (0.824–0.959) | 78.38 | 100.0 | – | 0.216 | 100.0 | 90.80 | 32.0 |
| Extrapulmonary samples | ||||||||
| Smear | – | – | – | – | – | – | – | – |
| Mycobacteria culture | – | – | – | – | – | – | – | – |
| Cobas MTB | 0.905 (0.740–0.999) | 83.33 | 97.67 | 35.83 | 0.170 | 83.30 | 97.70 | 12.0 |
| Logix Smart MTB | 0.974 (0.939–0.999) | 100.0 | 94.87 | 19.5 | 0.000 | 100.0 | 100.0 | 16.0 |
AUC, area under the curve; MTB, Mycobacterium tuberculosis; ROC, receiver operating characteristic; LHR, Likelihood ratio; 95% CI, 95% confidence interval.