Table 2.
Diagnostic Accuracy of the BD MAX Assay for Detection of Mycobacterium tuberculosis Among Raw Specimens Against a Microbiological Reference Standard of Mycobacterial Culture
| Microbiological Culture | |||
|---|---|---|---|
| Analysis and BD MAX Result | Positive | Negative | Total (95% CI) |
| Overall | |||
| Positive | 262 | 17 | 279 (PPV, 94% [91–96%]) |
| Negative | 20 | 593 | 613 (NPV, 97% [95–98%]) |
| Total | 282 | 610 | 892 |
| Sensitivity | 93% (89–95%)a | ||
| Specificity | 97% (96–98%)a | ||
| Smear stratifiedb | |||
| FM smear positive | |||
| Positive | 175 | 1 | 176 (PPV, 99% [97–100%]) |
| Negative | 0 | 0 | 0 |
| Total | 175 | 1 | 176 |
| Sensitivity | 100% (98–100) | ||
| Specificity | … | ||
| FM smear negative | |||
| Positive | 87 | 15 | 102 (PPV, 85% [77–91%]) |
| Negative | 20 | 591 | 611 (NPV, 97% [95–98%]) |
| Total | 107 | 606 | 713 |
| Sensitivity | 81% (73–88%) | ||
| Specificity | 98% (96–99%) | ||
| ZN smear positive | |||
| Positive | 148 | 0 | 148 (PPV, 100% [98–100%]) |
| Negative | 0 | 0 | 0 (NPV, 100% [21–100%]) |
| Total | 148 | 0 | 148 |
| Sensitivity | 100% (98–100%) | ||
| Specificity | … | ||
| ZN smear negative | |||
| Positive | 114 | 16 | 130 (PPV, 88% [81–92%]) |
| Negative | 20 | 592 | 612 (NPV, 97% [95–98%]) |
| Total | 134 | 608 | 742 |
| Sensitivity | 85% (78–90%) | ||
| Specificity | 97% (96–98%) | ||
Abbreviations: BD MAX, BD MAX multidrug-resistant tuberculosis assay; CI, confidence interval; FM, fluorescence microscopy; NPV, negative predictive value; PPV, positive predictive value; ZN, Ziehl-Neelsen.
aUsing a composite reference standard consisting of Xpert and mycobacterial culture, sensitivity was 93% (275/297 [89–95%]) and specificity was 99% (584/592 [97–99%]).
bSmears performed from raw specimens. Two specimens had a smear status unknown for ZN and 3 specimens had a smear status unknown for FM.