Table 4.
Sensitivity and specificity of the LAM test, sputum smear microscopy and combinations of the tests
| Total | Sensitivity | Specificity | LR (+) | LR (−) | PPV | NPV | |||
|---|---|---|---|---|---|---|---|---|---|
| N | % (95 % CI) | N | % (95 % CI) | % (95 % CI) | % (95 % CI) | % (95 % CI) | % (95 % CI) | ||
| LAM test | 469 | 24/55 | 44 (30–58) | 393/414 | 95 (92–97) | 8.6 (5.1-14.4) | 0.6 (0.5-0.8) | 53 (38–68) | 93 (90–95) |
| ZN microscopy | 467 | 29/55 | 53 (39–66) | 406/412a | 99 (97–100) | 36.2 (15.7-83.3) | 0.5 (0.4-0.6) | 83 (66–93) | 94 (91–96) |
| ZN + Fluorescence microscopy | 467 | 31/55 | 56 (42–70) | 406/412a | 99 (97–100) | 38.7 (16.9-88.5) | 0.4 (0.3-0.6) | 84 (68–94) | 94 (92–96) |
| LAM + ZN microscopy | 469 | 34/55 | 62 (48–75)a | 388/414 | 94 (90–96)a,b | 9.8 (6.4-15.1) | 0.4 (0.3-06) | 57 (43–69) | 95 (92–97) |
| LAM + ZN + Fluorescence Microscopy | 469 | 35/55 | 64 (50–76)a | 388/414 | 94 (91–96)a,c | 10.1 (6.6-15.5) | 0.4 (0.3-0.6) | 57 (44–70) | 95 (93–97) |
For combinations of test a positive result was recorded if any of the tests were positive
a p < 0.05 for comparison with LAM test alone
b p < 0.05 for comparison with ZN microscopy alone
c p < 0.05 for comparison with ZN + Fluorescence microscopy
LR (+) = Positive Likelihood Ratio, LR (−) = Negative Likelihood Ratio, PPV = Positive Predictive Value, NPV = Negative Predictive Value, ZN = Ziehl Neelsen