Table 2. Test performance (including comparison to clinical case definitions) for smear microscopy, MGIT culture, MTBDRplus directly on sputum, LCTB, and Xpert MTB/RIF assays stratified by smear microscopy and HIV status.
| Test Performance Measurea | Smear Microscopy | MGIT Culture | NAAT Performed Directly on Sputum | ||
| MDRTBplus | LCTB | Xpert MTB/RIF | |||
| Comparison to MGIT culture ( n = 177) | |||||
| Sensitivity | 59 (47–71) | NA | 76 (64–85) | 76 (64–85) | 86 (76–93) |
| Specificity | 100 (96–100) | 97 (92–99) | 98 (93–99) | 97 (92–99) | |
| PPV | 100 (91–100) | 94 (84–98) | 92 (87–99) | 95 (86–99) | |
| NPV | 80 (72–86) | 87 (79–92) | 87 (79–92) | 92 (85–96) | |
| Comparison to MGIT culture (HIV-positive cohort only, n = 124) | |||||
| Sensitivity | 54 (38–69) | NA | 70 (54–83) | 70 (54–83) | 84 (69–93) |
| Specificity | 100 (95–100) | 96 (89–99) | 98 (93–100) | 96 (89–99) | |
| PPV | 100 (85–100) | 91 (76–98) | 97 (83–100) | 92 (79–98) | |
| NPV | 80 (70–87) | 85 (76–92) | 86 (77–92) | 92 (84–97) | |
| Comparison to MGIT culture (HIV-negative cohort only, n = 26) | |||||
| Sensitivity | 66 (35–90) | 75 (43–95) | 75 (42–94) | 83 (52–98) | |
| Specificity | 100 (70–100) | 100 (76–100) | 100 (76–100) | 100 (76–100) | |
| PPV | 100 (63–100) | 100 (66–100) | 100 (66–100) | 100 (69–100) | |
| NPV | 79 (52–93) | 82 (56–96) | 82 (56–96) | 88 (62–98) | |
| Comparison to clinical case definition “Any TB including definite, probable, and possible TB” ( n = 177) | |||||
| Sensitivity | 40 (30–50) | 66 (56–75) | 51 (40–60) | 51 (40–60) | 58 (48–68) |
| Specificity | 100 (95–100) | 100 (95–100) | 96 (88–99) | 97 (91–99) | 97 (91–99) |
| PPV | 100 (91–100) | 100 (94–100) | 94 (84–98) | 96 (87–99) | 97 (88–99) |
| NPV | 56 (47–64) | 69 (59–77) | 59 (50–68) | 60 (51–68) | 63 (54–72) |
| Percent detection b | |||||
| Smear-positive, culture-positivec, number/total (percent) | 40/49 (81) | 49/49 (100) | 46/49 (94) | 47/49 (96) | 47/49 (96) |
| Smear-negative, culture-positived, number/total (percent) | 0/18 (0) | 18/18 (100) | 5/18 (28) | 4/18 (22) | 11/18 (61) |
| Smear-negative, culture-negative, number/total (percent) | 0/107 (0) | 0/107 (0) | 3/107 (3) | 1/107 (1) | 3/107 (3) |
All tests performed on the same 177 sputum specimens. Confidence intervals 95%.
a
All values are percent (95% CI) unless otherwise indicated.
HIV status distribution was as follows: HIV-positive, 124; HIV-negative 26; HIV status unknown, 27.
b
Amongst 177 cases where all tests were done, 49 were smear-positive, culture-positive; 18 were smear-negative, culture-positive; 107 were smear-negative, culture-negative; in three cases NTM was isolated.
c
Where any of the three smears taken during the study period were positive.
d
Where all of the three smears taken during the study period were negative.