TABLE 2.
Accuracy of conventional and 1:10 dilution methods of MTD testing
| AFB smear microscopy result and MTD method | MTD result(s) | No. of specimens with culture result of:
|
Total no. of specimens | Sensitivity (%) (95% CI) | Specificity (%) (95% CI) | PPV (%) (95% CI) | NPV (%) (95% CI) | ||
|---|---|---|---|---|---|---|---|---|---|
| Positive for M. tuberculosis complex | Positive for NTM | Negative | |||||||
| Positive | |||||||||
| Conventional | Positive | 94 | 2 | 2 | 98 | 83.2 (78.0-88.4) | 95.2 (92.2-98.2) | 95.9 (93.1-98.7) | 84.2 (79.1-89.3) |
| Negative | 15 | 66 | 14 | 95 | |||||
| Equivocal | 4 | 0 | 0 | 4 | |||||
| All | 113 | 68 | 16 | 197 | |||||
| 1:10 dilution | Positive | 112 | 1 | 2 | 115 | 99.1 (97.8-100) | 95.2 (92.2-98.2) | 97.4 (95.2-99.6) | 98.8 (97.3-100) |
| Negative | 1 | 66 | 14 | 81 | |||||
| Equivocal | 0 | 1 | 0 | 1 | |||||
| All | 113 | 68 | 16 | 197 | |||||
| Negative | |||||||||
| Conventional | Positive | 14 | 0 | 3 | 17 | 50.0 (44.3-55.7) | 97.7 (96.0-99.4) | 82.4 (78.0-86.8) | 96.3 (94.1-98.5) |
| Negative | 10 | 19 | 241 | 270 | |||||
| Equivocal | 4 | 0 | 3 | 7 | |||||
| All | 28 | 19 | 247 | 294 | |||||
| 1:10 dilution | Positive | 13 | 0 | 1 | 14 | 46.4 (40.7-52.1) | 99.6 (98.9-100) | 92.9 (90.0-95.8) | 95.3 (92.9-97.7) |
| Negative | 13 | 19 | 246 | 278 | |||||
| Equivocal | 2 | 0 | 0 | 2 | |||||
| All | 28 | 19 | 247 | 294 | |||||