Table 2 Sensitivity and specificity of smear microscopy and chest-x-ray for M.tb and NTM by HIV status
|  |  | HIV positive (n = 219) | HIV negative (n = 733) | ||
|---|---|---|---|---|---|
|  |  | M.tb (n = 69) | NTM (n = 26) | M.tb (n = 185) | NTM (n = 39) |
% (95% CI) | % (95% CI) | % (95% CI) | % (95% CI) | ||
Sputum smear test for all TB suspects | Sensitivity | 49.3 [42.7-55.9] | 7.7 [3.4-12.0] | 69.7 [66.4-73.0] | 10.3 [7.8-12.8] |
Specificity | 81.3 [78.6-83.7] | 78.7 [75.9-81.2] | 90.9 [88.6-92.7] | 78.6 [75.9-81.2] | |
PPV | 17.1 [12.5-22.9] | 1.0 [0.3-3.6] | 64.8 [58.0-71.1] | 2.0 [0.8-5.1] | |
NPV | 95.4 [93.6-96.4] | 96.8 [95.3-97.9] | 92.6 [90.5-94.2] | 95.4 [93.6-96.6] | |
Chest-x-ray for smear-negative TB suspects | Net sensitivity | 78.3 [72.3-84.3] | 42.3 [34.2-50.4] | 90.3 [87.9-92.7] | 48.7 [44.4-53.0] |
Net specificity | 65.9 [62.7-68.7] | 62.9 [59.7-65.9] | 75.5 [72.3-78.4] | 63.2 [60.0-66.3] | |
Net PPV | 15.2 [14-16.3] | 3.1 [2.6-3.7] | 47.0 [45.4-48.6] | 5.4 [4.7-6.1] | |
Net NPV | 97.5 [96.1-98.6] | 97.5 [97.1-97.8] | 97.0 [96.6-97.4] | 96.6 [96.1-97.0] | |
Incremental yield | 29.0 [22.4-35.7] | 34.6 [26.8-42.4] | 20.6 [17.3-23.9] | 38.4 [34.2-42.6] | |