Table 3.
Effects of smear positivity after decontamination, storage time of sputum, and sputum volume on time to detection of M. tuberculosis growthb
| Predictor | BacT/Alert 3D system |
L-J medium |
Gottsacker medium |
||||||
|---|---|---|---|---|---|---|---|---|---|
| No. (%) of positive samples | Median TTD (days) (range) | P (trend) | No. (%) of positive samples | Median TTD (days) (range) | P (trend) | No. (%) of positive samples | Median TTD (days) (range) | P (trend) | |
| Smear positivity score | |||||||||
| Doubtful | 3 (1.2) | 26 (21–40) | <0.001 | 4 (1.6) | 45 (28–60) | 0.065 | 1 (0.4) | 60 (60–60) | 0.845 |
| 1+ | 11 (4.4) | 23 (15–48) | 8 (3.2) | 31 (20–60) | 7 (3.0) | 60 (20–60) | |||
| 2+ | 34 (13.5) | 18 (6–39) | 31 (12.4) | 22 (15–60) | 23 (9.7) | 22 (15–30) | |||
| 3+ | 73 (29.1) | 16 (6–46) | 74 (29.7) | 22 (11–60) | 68 (28.8) | 22 (11–60) | |||
| 4+ | 138 (51.8) | 10 (6–30) | 132 (53.0) | 18 (10–49) | 137 (58.1) | 18 (10–60) | |||
| Totala | 251 (100.0) | 14 (6–48) | 249 (100.0) | 19 (10–60) | 236 (100.0) | 19 (10–60) | |||
| Storage time (days) | |||||||||
| 16–30 | 6 (2.4) | 11 (6–15) | <0.001 | 7 (2.8) | 19 (17–22) | 0.208 | 7 (3.0) | 19 (17–22) | 0.177 |
| 31–60 | 12 (4.8) | 8 (6–15) | 15 (6.0) | 17 (14–60) | 15 (6.4) | 17 (14–28) | |||
| 61–90 | 41 (16.3) | 10 (6–48) | 41 (16.5) | 18 (10–30) | 40 (16.9) | 18 (10–29) | |||
| 91–120 | 53 (21.1) | 11 (6–23) | 58 (23.3) | 19 (11–49) | 59 (25.0) | 19 (11–60) | |||
| 121–150 | 49 (19.5) | 15 (6–42) | 51 (20.5) | 22 (12–60) | 43 (18.2) | 22 (12–60) | |||
| 151–180 | 90 (35.9) | 18 (8–46) | 77 (30.9) | 23 (15–60) | 72 (30.5) | 23 (15–60) | |||
| Total | 251 (100.0) | 14 (6–48) | 249 (100.0) | 19 (10–60) | 236 (100.0) | 19 (10–60) | |||
| Sputum vol (ml) | |||||||||
| 0.5 | 8 (3.2) | 26 (17–46) | <0.001 | 7 (2.8) | 25 (24–60) | 0.008 | 4 (1.7) | 43 (24–60) | 0.674 |
| 1 | 38 (15.1) | 22 (6–36) | 34 (13.7) | 24 (10–60) | 28 (11.9) | 24 (10–60) | |||
| 1.5 | 32 (12.8) | 21 (13–40) | 27 (10.8) | 27 (17–60) | 23 (9.7) | 27 (17–60) | |||
| 2 | 35 (13.9) | 12 (7–48) | 34 (13.7) | 18 (11–49) | 33 (14.0) | 18 (11–60) | |||
| 3 | 25 (10.0) | 13 (7–30) | 26 (10.4) | 19 (10–38) | 26 (11.0) | 21 (10–60) | |||
| 4 | 14 (5.6) | 13 (6–42) | 14 (5.6) | 21 (12–36) | 12 (5.1) | 20 (11–33) | |||
| 5 | 99 (39.4) | 10 (6–35) | 107 (43.0) | 18 (10–60) | 110 (46.6) | 18 (10–60) | |||
| Total | 251 (100.0) | 14 (6–48) | 249 (100.0) | 19 (10–60) | 236 (100.0) | 19 (10–60) | |||
a
P < 0.001 for the BacT/Alert system versus L-J medium and P < 0.001 for the BacT/Alert system versus Gottsacker medium (by Wilcoxon matched-pairs test).
b
n = 319. TTD, time to detection of M. tuberculosis growth in days.