Table 3. Incidence of active TB among subjects with LTBI stratified by age and TST and QFT-GIT assay results (n = 1511).
| Age group | TB cases N (%) | Incidence proportion | Person-years | Incidence rate [1000 person-years] (CI) |
|---|---|---|---|---|
| 1–14 (n = 456) | 20 (26.32) | 4.39 | 10747.23 | 1.86 (1.20–2.88) |
| 15–24 (n = 435) | 27 (35.53) | 6.21 | 10214.13 | 2.64 (1.81–3.85) |
| 25–34 (n = 146) | 16 (21.05) | 6.81 | 5491.9 | 2.91 (1.78–4.76) |
| 35–44 (n = 146) | 06 (7.89) | 4.11 | 3434.83 | 1.75 (0.78–3.89) |
| 45–55 (n = 163) | 04 (5.26) | 2.45 | 3884.9 | 1.03 (0.39–2.74) |
| 55–65 (n = 63) | 03 (3.95) | 3.95 | 1799.1 | 1.76 (0.57–5.46) |
| TST+ (n = 732) | 42 (55) | 5.74 | 18515.83 | 2.26 (1.68–3.07) |
| QFT-GIT+ (n = 917) | 56 (74) | 6.11 | 21515.27 | 2.60 (2.00–3.38) |
| TST- (n = 779) | 34 (45) | 4.36 | 17056.27 | 1.99 (1.42–2.79) |
| QFT-GIT- (n = 581) | 19 (25) | 3.27 | 13756.73 | 1.38 (0.88–2.16) |
| TST+QFT-GIT+ (n = 540) | 29 (38) | 5.37 | 14149.77 | 2.15 (1.42–2.94) |
| TST+ QFT-GIT- (n = 187) | 13 (17) | 6.95 | 4366.07 | 2.98 (1.75–5.13) |
| TST-QFT-GIT+ (n = 377) | 28 (37) | 7.42 | 7569.6 | 3.70 (2.55–5.36) |
| TST-QFT-GIT- (n = 394) | 06 (08) | 1.52 | 9390.67 | 0.64 (0.29–1.42) |
| Total (n = 1511) | 76 (100) | 5.03 | 35572.1 | 2.14 (1.71–2.67) |
Note. TB = tuberculosis; CI = confidence interval; TST = tuberculin skin test; QFT-GIT = QuantiFERON-TB®Gold In-Tube.