Table 2.
Relative diagnostic efficiencies of smear microscopy, Xpert Ultra, Xpert G4 and LPA tests in detecting Mycobacterium tuberculosis from pulmonary and extra-pulmonary samples.
| Parameter | Auramine | Xpert Ultra | Xpert G4 | LPA |
|---|---|---|---|---|
| Pulmonary samples | ||||
| True Positive | 41 | 44 | 39 | 40 |
| True Negative | 65 | 41 | 65 | 8 |
| False Positive | 7 | 29 | 7 | 64 |
| False Negative | 9 | 6 | 10 | 10 |
| Total | 122 | 120 ‡ | 121 § | 122 |
| Sensitivity (CI), % | 82,00 (68,56-91,42) | 88,00 (75,69-95,47) | 79,59 (65,66-89,76) | 80,00 (66,28-89,97) |
| Specificity (CI), % | 90,28 (80,99-96,00) | 58,57 (46,17-70,23) | 90,28 (80,99-96,00) | 11,11 (4,92-20,72) |
| Positive predictive value (CI), % | 85,42 (74,11-92,30) | 60,27 (53,00-67,12) | 84,78 (73,10-91,95) | 38,46 (34,73-42,33) |
| Negative predictive value (CI), % | 87,84 (79,91-92,91) | 87,23 (75,87-93,69) | 86,67 (78,81-91,91) | 44,44 (25,35-65,33) |
| Extra-pulmonary samples | ||||
| True Positive | 7 | 9 | 6 | 9 |
| True Negative | 66 | 33 | 65 | 17 |
| False Positive | 1 | 34 | 2 | 50 |
| False Negative | 6 | 4 | 6 | 4 |
| Total | 80 | 80 | 79 + 1 ** | 80 |
| Sensitivity (CI), % | 53,85 (25,13-80,78) | 69,23 (38,57-90,91) | 50,00 (21,09-78,91) | 69,23 (38,57-90,91) |
| Specificity (CI), % | 98,51 (91,96-99,96) | 49,25 (36,82-61,76) | 97,01 (89,63-99,64) | 25,37 (15,53-37,49) |
| Positive predictive value (CI), % | 87,50 (48,41-98,12) | 20,93 (14,66-28,97) | 75,00 (40,63-92,93) | 15,25 (10,88-20,98) |
| Negative predictive value (CI), % | 91,67 (85,94-95,19) | 89,19 (77,89-95,08) | 91,55 (86,00-95,03) | 80,95 (63,04-91,37) |
†3 Samples were contaminated and discarded; adding the 3 contaminated isolates equals 205.
‡2 Isolates were invalid. Adding them will amount to 122.
§1 Isolate was in error, adding it will make up to 122.
**1 isolate was invalid. Adding it will amount to 80; # 1 isolate was in error, adding it will make up to 122.