TABLE 2.
Molecular assay performance compared with reference testing for the diagnosis of TBa
| Performance measurement | Percentage (95% CI) for tests performed on: |
||||||
|---|---|---|---|---|---|---|---|
| Pellets (SOC) |
Sputa (direct) |
Pellets |
|||||
| Sputum 3 |
Sputum 1 (SOC) |
Sputum 2 |
Sputum 4 |
Sputum 3 |
|||
| Smear microscopy | MGIT culture | Xpert MTB/RIF, visit 1 | Abbott RealTime MTB assay, visit 1 | Abbott RealTime MTB assay, visit 2 | Xpert MTB/RIF, visit 2 | Abbott RealTime MTB assay, visit 2 | |
| Comparison with MGIT culture (n = 193) | |||||||
| Sensitivity | 43.5 (31.7–56.7) | 79.0 (66.8–88.3) | 83.9 (72.3–92.0) | 88.7 (78.1–95.3) | 91.9 (82.2–97.3) | 85.5 (74.2–93.1) | |
| Specificity | 98.5 (94.6–99.8) | 96.9 (92.4–99.2) | 92.3 (86.3–96.2) | 94.6 (89.2–97.8) | 97.7 (93.5–99.5) | 92.4 (86.4–96.3) | |
| PPV | 93.1 (77.2–99.2) | 92.5 (81.8–97.9) | 83.9 (72.3–92.0) | 88.7 (78.1–95.3) | 95.0 (86.1–99.0) | 84.1 (7278–92.1) | |
| NPV | 78.7 (71.6–84.7) | 90.7 (84.6–95.0) | 92.3 (86.3–96.2) | 94.6 (89.2–97.8) | 96.2 (91.4–98.8) | 93.1 (87.3–96.8) | |
| Comparison with MGIT culture (HIV-positive cohort only) (n = 142)$ | |||||||
| Sensitivity | 37.5 (22.7–54.2) | 70.0 (53.5–83.4) | 75.0 (58.8–87.3) | 82.5 (67.2–92.7) | 87.5 (73.2–95.8) | 77.5 (61.5–89.2) | |
| Specificity | 98.0 (93.1–99.8) | 96.1 (90.3–98.9) | 93.1 (86.2–97.2) | 95.1 (88.9–98.4) | 97.1 (91.6–99.4) | 93.1 (86.4–97.2) | |
| PPV | 88.2 (63.6–98.5) | 87.5 (71.0–96.5) | 81.1 (64.8–92.0) | 86.8 (71.9–95.6) | 92.1 (78.6–98.3) | 81.6 (65.7–92.3) | |
| NPV | 80.0 (71.9–86.6) | 89.1 (81.7–94.2) | 90.4 (83.0–95.3) | 93.3 (86.6–97.3) | 95.2 (89.1–98.4) | 91.3 (84.2–96.0) | |
| Comparison with MGIT culture (HIV-negative cohort only) (n = 44)$ | |||||||
| Sensitivity | 55.0 (31.5–76.9) | 95 (75.1–99.9) | 100 (83.2–100) | 100 (83.2–100) | 100 (83.2–100) | 100 (83.2–100) | |
| Specificity | 100 (86.3–100) | 100 (86.3–100) | 92.0 (74.0–99.0) | 91.7 (73.0–99.0) | 100 (86.3–100) | 88.0 (68.8–97.5) | |
| PPV | 100 (71.5–100) | 100 (82.4–100) | 90.9 (70.8–98.9) | 90.9 (70.8–98.9) | 100 (83.2–100) | 87.0 (66.4–97.2) | |
| NPV | 73.5 (55.6–87.1) | 96.2 (80.4–99.9) | 100 (85.2–100) | 100 (84.6–100) | 100 (86.3–100) | 100 (84.6–100) | |
| Comparison with clinical case definition# (Any TB including definite, possible, probable TB) (n = 202) | |||||||
| Sensitivity | 31.6 (22.4–41.9) | 74.7 (63.9–83.6) | 62.8 (52.2–72.5) | 61.7* (51.1–71.5) | 64.9 (54.4–74.5) | 67 (56.6–76.4) | 66 (55.5–75.4) |
| Specificity | 100 (96.6–100) | 100 (96.5–100) | 100 (96.6–100) | 95.3* (89.4–98.5) | 95.3 (89.4–98.5) | 100 (96.6–100) | 94.4 (88.3–97.9) |
| PPV | 100 (88.4–100) | 100 (94.2–100) | 100 (93.9–100) | 92.1* (82.4–97.4) | 92.4 (83.2–97.5) | 100 (94.3–100) | 91.2 (81.8–96.7) |
| NPV | 62.4 (54.8–69.7) | 83.1 (75.2–89.2) | 75.5 (67.6–82.3) | 73.9* (65.8–81.0) | 75.6 (67.4–82.5) | 77.7 (69.9–84.3) | 76.1 (68.0–83.1) |
a
*, test not done (n = 1); $, of the 193 MGIT results, there were 7 patients with an unknown HIV status, and these were excluded from the HIV stratification; #, reported to minimize differences between specimen collection and testing due to limited volume and SOC, return visits, and potential use of antibiotics.