Table 1.
Sensitivity and specificity in detection of MTBC by diagnostic test
| Diagnostic test | Positive culture as reference standard a | |||
|---|---|---|---|---|
| Sensitivity Culture-positive |
Specificity Culture-negative |
|||
| All culture- positive |
Smear- positive |
Smear- negative |
||
| N=109 | N=93 | N=16 | N=127 b | |
| Xpert, direct | ||||
| n/N (%) | 102/107c (95.3%) | 91/91c (100%) | 11/16 (68.8%) | 104/121d (86.0%) |
| 95% CI | 90.0–98.3% | 96.8–100% | 43.7–87.5% | 78.9–91.3% |
| Xpert, concentrated | ||||
| n/N (%) | 103/109 (94.5%) | 91/93 (97.9%) | 12/16 (75.0%) | 111/127 (87.4%) |
| 95% CI | 88.9–97.7% | 93.1–99.6% | 50.1–91.5% | 80.8–92.4% |
| Direct smear | ||||
| n/N (%) | 65/109 (59.6%) | 65/93 (69.9%) | 0/16 (0%) | 124/127 (97.6%) |
| 95% CI | 50.2–68.5% | 60.0–78.6% | 0–17.1% | 93.7–99.4% |
| Concentrated smear | ||||
| n/N (%) | 93/109 (85.3%) | 93/93 (100%) | 0/16 (0%) | 114/126g (90.5%) |
| 95% CI | 77.7–91.1% | 96.8–100% | 0–17.1% | 84.4–94.7% |
| LJ only | ||||
| n/N (%) | 84/104e (80.8%) | 77/89f (86.5%) | 7/15g (46.7%) | 125/125h (100%) |
| 95% CI | 72.4–87.5% | 78.2–92.5% | 21.5–68.1% | 97.6–100% |
| MGIT only | ||||
| n/N (%) | 107/109 (98.2%) | 92/92i (100%) | 15/15i (100%) | 116/116k (100%) |
| 95% CI | 94.1–99.7% | 96.8–100% | 81.9–100% | 97.5–100% |
| TB-Biochip (N=104)l | ||||
| n/N (%) | 69/71 (97.3%) | 64/64 (100%) | 5/7 (71.4%) | 25/32 (78.1%) |
| 95% CIi | 91.0–99.5% | 95.4–100% | 33.0–94.9% | 61.5–89.9% |
Note.
n=correct number of tests, compared to the reference standard.
N=total number of tests.
Reference standard: positive culture (either LJ and/or MGIT) in same specimen except as noted. For estimation of test performance, NTM were considered culture-negative.
One had both LJ and MGIT cultures contaminated; one culture result was missing.
Two were indeterminate.
Six were indeterminate.
Four cultures were contaminated, one culture result was missing.
Four cultures were contaminated.
One culture result was missing
Two culture results were missing.
One culture was contaminated.
Seven cultures were contaminated; four culture results were missing.
TB-Biochip was only performed at the CTRI laboratory on 104 specimens. A total of 71/104 specimens were MTBC culture-positive (64/71 smear-positive); 100/104 specimens were from patients with culture-confirmed or final diagnosis of TB and 4/104 specimens were from patients with ruled out TB.