Table 1.
Performance of acid-fast bacilli smears for diagnosing pulmonary tuberculosis.
| Accumulated AFB smears (N) | Accumulated samples (N) | Sensitivity % (95% CI) | Positive/total | Specificity% (95% CI) | Negative/total | PPV % (95% CI) | NPV % (95% CI) |
|---|---|---|---|---|---|---|---|
| 1 | 7,155 | 24.6 (21.2-27.9) | 156/635 | 99.6 (99.4-99.7) | 6,492/6,520 | 84.8 (79.6-90.0) | 93.1 (92.5-93.7) |
| 2 | 10,688 | 33.4 (29.7-37.1) | 212/635 | 99.5 (99.3-99.7) | 6,487/6,520 | 86.5 (82.3-90.8) | 93.9 (93.3-94.4) |
| 3 | 12,160 | 36.2 (32.5-40.0) | 230/635 | 99.5 (99.3-99.6) | 6,485/6,520 | 86.8 (82.7-90.9) | 94.1 (93.6-94.7) |
| 4 | 12,993 | 37.3 (33.6-41.1) | 237/635 | 99.5 (99.3-99.6) | 6,484/6,520 | 86.8 (82.8-90.8) | 94.2 (93.7-94.8) |
| 5 | 13,282 | 37.6 (33.9-41.4) | 239/635 | 99.4 (99.2-99.6) | 6,482/6,520 | 86.3 (82.2-90.3) | 94.2 (93.7-94.8) |
| 6 | 13,419 | 38.0 (34.2-41.7) | 241/635 | 99.4 (99.2-99.6) | 6,481/6,520 | 86.1 (82.1-90.1) | 94.3 (93.7-94.8) |
| 7 | 13,488 | 38.0 (34.2-41.7) | 241/635 | 99.4 (99.2-99.6) | 6,481/6,520 | 86.1 (82.1-90.1) | 94.3 (93.7-94.8) |
| 8 | 13,526 | 38.0 (34.2-41.7) | 241/635 | 99.4 (99.2-99.6) | 6,481/6,520 | 86.1 (82.1-90.1) | 94.3 (93.7-94.8) |
A total of 7,155 patients, who had 1-8 BALF and/or sputum AFB smears, as well as BALF and/or sputum cultures (single or multiple per person) performed simultaneously during hospitalization, were included in the analysis. Pulmonary tuberculosis was defined as at least one of the BALF and/or sputum specimens having one positive culture result for M. tuberculosis. AFB, acid-fast bacilli; PPV, positive predictive value; NPV, negative predictive value; CI, confidence interval; BALF, bronchoalveolar lavage fluid.