Table 2.
Accuracy of Xpert Mycobacterium tuberculosis/Rifampicin and Smear on Induced Sputum Compared With Liquid Culture
| Sensitivity | Specificity | PPV | NPV | Sensitivity for Smear-Positive Samples | Sensitivity for Smear-Negative Samples | |
|---|---|---|---|---|---|---|
| All children with complete results from at least one IS and NPA specimen (n = 535) | ||||||
| Xpert | ||||||
| All | 64/87, 73.6 (64.1–83.0) | 443/448, 98.9 (97.9–99.9) | 92.8 | 95.1 | 29/30, 96.7 (89.9–100) | 35/57, 61.4 (48.4–74.4) |
| HIV infected (n = 117) | 14/15, 93.3 (79.0–100) | 102/102, 100 (96.4–100) | 100 | 99.0 | 9/9, 100 (66.4–100) | 5/6, 83.3 (40.5–100) |
| HIV uninfected (n = 417) | 50/72, 69.4 (58.5–80.3) | 340/345, 98.6 (97.3–99.8) | 90.9 | 93.9 | 20/21, 95.2 (85.3–100) | 30/51, 58.8 (44.8–72.8) |
| Smear microscopy | 28/87, 32.2 (22.2–42.2) | 448/448, 100 (99.2–100) | 100 | 88.4 | ||
| Children with complete results from two paired IS and NPA specimens (n = 396) | ||||||
| Xpert (first IS specimen) | 36/63, 57.1 (44.6–69.7) | 332/333, 99.7 (99.1–100) | 97.3 | 92.5 | 21/21, 100 (83.9–100) | 15/42, 35.7 (20.6–50.8) |
| Xpert (both IS specimens) | ||||||
| All | 45/63, 71.4 (60.0–82.9) | 330/333, 99.1 (98.1–100) | 93.8 | 94.8 | 21/21, 100 (83.9–100) | 24/42, 57.1 (41.5–72.8) |
| HIV infected (n = 80) | 7/8, 87.5 (57.9–100) | 72/72, 100 (95.0–100) | 100 | 98.6 | 6/6, 100 (54.1–100) | 1 / 2, 50 ( − 5.9–6.9) |
| HIV uninfected (n = 315) | 38/55, 69.1 (56.5–81.7) | 257/260, 98.8 (97.6–100) | 92.7 | 93.8 | 15/15, 100 (78.2–100) | 23/40, 57.5 (41.5–73.5) |
| Smear microscopy (two smears) | 21/63, 33.3 (21.4–45.3) | 333/333, 100 (99.0–100) | 100 | 88.8 | ||
Data are the number correct/number tested, % (95% confidence interval).
Abbreviations: HIV, human immunodeficiency virus; IS, induced sputum; NPA, nasopharyngeal aspirate; NPV, negative predictive value; PPV, positive predictive value.