Table 2.
Performance of Xpert MTB/RIF in different specimens
| Specimen type | No. (%) | Xpert positive cases (%) | Confirmed TB (%) | Sensitivity (95% CI) (%) | Specificity (95% CI) (%) | Positive predictive value (95% CI) (%) | Negative predictive value (95% CI) (%) |
|---|---|---|---|---|---|---|---|
| Presumptive PTB cases | 533 (67.7%) | 48 (9.0%) | 52 (9.8%) | 88.5 (77.0–94.6) | 99.6 (98.5–99.9) | 95.8 (86.0–98.9) | 98.8 (97.3–99.4) |
| BALF | 204 (25.9%) | 7 (3.4%) | 7 (3.4%) | 85.7 (48.7–97.4) | 99.5 (97.2–99.9) | 85.7 (48.7–97.4) | 99.5 (97.2–99.9) |
| Sputum | 165 (21.0%) | 24 (14.5%) | 26 (15.8%) | 88.5 (71.0–96.0) | 99.3 (96.0–99.9) | 95.8 (79.8–99.3) | 97.9 (93.9–99.3) |
| FOB | 105 (13.3%) | 9 (8.6%) | 11 (10.5%) | 81.2 (52.3–94.9) | 100.0 (96.1–100.0) | 100.0 (70.1–100.0) | 97.9 (92.7–99.4) |
| Lung tissue | 52 (6.6%) | 7 (13.5%) | 7 (13.5%) | 100.0 (64.6–100.0) | 100.0 (92.1–100.0) | 100.0 (64.6–100.0) | 100.0 (92.1–100.0) |
| Others | 7 (0.9%) | 1 (14.3%) | 1 (14.3%) | 100.0 (20.7–100.0) | 100.0 (61.0–100.0) | 100.0 (20.7–100.0) | 100.0 (61.0–100.0) |
| Presumptive EPTB cases | 172 (21.9%) | 14 (8.1%) | 17 (9.9%) | 76.5 (52.7–90.4) | 99.4 (96.4–99.9) | 92.9 (68.5–98.7) | 97.5 (93.7–99.0) |
| Intestine tissue | 53 (6.7%) | 1 (1.9%) | 0 (0%) | NA# | 98.1 (90.1–99.7) | 0.0 (0.0–79.4) | 100.0 (93.1–100.0) |
| CSF | 42 (5.3%) | 2 (4.8%) | 2 (4.8%) | 100.0 (34.2–100.0) | 100.0 (91.2–100.0) | 100.0 (34.2–100.0) | 100.0 (91.2–100.0) |
| Ascitic fluid | 18 (2.3%) | 0 (0%) | 0 (0%) | NA | 100.0 (82.4–100.0) | NA | 100.0 (82.4–100.0) |
| Joint cavity fluid | 13 (1.7%) | 2 (15.4%) | 2 (15.4%) | 100.0 (34.2–100.0) | 100.0 (74.1–100.0) | 100.0 (34.2–100.0) | 100.0 (74.1–100.0) |
| Extrapulmonary lymph node | 12 (1.5%) | 5 (41.7%) | 5 (41.7%) | 100.0 (56.6–100.0) | 100.0 (64.6–100.0) | 100.0 (56.6–100.0) | 100.0 (64.6–100.0) |
| Urine | 11 (1.4%) | 1 (9.1%) | 3 (27.3%) | 33.3 (6.2–79.2) | 100.0 (67.6–100.0) | 100.0 (20.7–100.0) | 80.0 (49.0–94.3) |
| Others | 23 (2.9%) | 3 (13.0%) | 5 (21.7%) | 60.0 (23.1–88.2) | 100.0 (82.4–100.0) | 100.0 (43.9–100.0) | 90.0 (69.9–97.2) |
| Presumptive TP cases | 82 (10.4%) | 3 (3.7%) | 20 (24.4%) | 15.0 (5.2–36.0) | 100.0 (94.2–100.0) | 100.0 (43.9–100.0) | 78.5 (68.2–86.1) |
| Pleural fluid | 82 (10.4%) | 3 (3.7%) | 20 (24.4%) | 15.0 (5.2–36.0) | 100.0 (94.2–100.0) | 100.0 (43.9–100.0) | 78.5 (68.2–86.1) |
| Total | 787 | 65 (8.3%) | 89 (11.3%) | 69.7 (59.5–78.2) | 99.6 (98.7–99.9) | 95.4 (87.3–98.4) | 96.3 (94.6–97.4) |
Abbreviation: PTB pulmonary tuberculosis; EPTB extra-pulmonary tuberculosis; TP tuberculous pleurisy; CI confidence interval; BALF bronchoalveolar lavage fluid; FOB Fiberoptic bronchoscopy; CSF Cerebrospinal fluid. #, NA, No Xpert positive results (and no confirmed TB cases) were obtained, thus the sensitivity (and positive predictive value) was not available