Table 4. Performance characteristics of the GeneXpert assay compared to drug susceptibility testing for rifampicin (RIF).
| TBw/oHIV & TB-HIV | TBw/oHIV | TB-HIV | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Xpert MTB/RIF | DST-RIF resistant | DST-RIF sensitive | Total | PPV(%) | NPV(%) | DST-RIF resistant | DST-RIF sensitive | Total | PPV(%) | NPV(%) | DST-RIF resistant | DST-RIF sensitive | Total | PPV(%) | NPV(%) |
| GX-RIF(+) | 120 | 36 | 156 | 76.9 | 119 | 35 | 154 | 77.3 | 1 | 1 | 2 | 50 | |||
| GX-RIF(-) | 28 | 628 | 656 | 95.7 | 26 | 612 | 638 | 95.9 | 2 | 16 | 18 | 88.9 | |||
| Total | 148 | 664 | 812 | 145 | 647 | 792 | 3 | 17 | 20 | ||||||
| Sensitivity(%) | 81.1 | 82.1 | 33.3 | ||||||||||||
| Specificity(%) | 94.6 | 94.6 | 94.1 | ||||||||||||
DST, drug susceptibility testing; MTB, Mycobacterium tuberculosis; RIF, rifampicin; GX, GeneXpert; NPV, negative predictive value; PPV, positive predictive value.