Latent tuberculosis infection (LTBI) treatment and active TB outcomes of individuals testing positive in the tuberculin skin test (TST+) in British Columbia Centre for Disease Control clinics, by year of first positive TST
| 2004–2008 | 2010–2014 | ||||
| All TST+ | All TST+ | TST+ only | TST+ and IGRA+ | TST+ and IGRA− | |
| Population | 12 406 | 10 342 | 6783 | 1369 | 2190 |
| LTBI treatment | |||||
| Started LTBI treatment (TST+) | 3699 (29.8)¶ | 2144 (20.7)¶ | 1216 (17.9)ƒ | 862 (63.0)ƒ | 66 (3.0) |
| Completed LTBI treatment (TST+) | 2158 (17.4)+ | 1565 (15.1)+ | 919 (13.5)## | 616 (45.0)## | 30 (1.4) |
| Completed LTBI treatment (started treatment) | 2158 (58.3)§ | 1565 (73.0)§ | 919 (75.6)¶¶ | 616 (71.5)¶¶ | 30 (45.5) |
| Active TB | |||||
| Active TB cases in follow-up | 22 | 19 | 17 | 2 | 0 |
| Length of follow-up person-years | 35 946 | 32 479 | 22 227 | 4019 | 6233 |
| Incidence of active TB per 105 person-years | 61.2 (35.6–86.8) | 58.5 (32.2–84.8) | 76.5 (40.1–112.8) | 49.8 (0–118.7) | 0 |
| Active TB cases, untreated# | 18 | 16 | 14 | 2 | 0 |
| Follow-up, untreated, person-years | 25 244 | 19 518 | 18 073 | 1445 | 6015 |
| Incidence untreated active TB per 105 person-years | 71.3 (38.3–104.2) | 82.0 (41.8–122.1) | 77.4 (36.9–118.0) | 138.4 (0–330.2) | 0 |
Data are presented as n, n (%) or rate (95% CI). IGRA: interferon-γ release assay #: any individuals in the study cohort who did not initiate therapy; ¶: proportion of TST+ individuals that started therapy pre-IGRA versus post-IGRA (Chi-squared 243.9, df=1, p<0.001); +: proportion of all TST+ individuals who started that completed therapy pre-IGRA versus post-IGRA (Chi-squared 21.1, df=1, p<0.001); §: proportion of all individuals that completed LTBI therapy pre-IGRA versus post-IGRA (Chi-squared 126.1, df=1, p<0.001); ƒ: proportion of TST+ only versus TST+/IGRA individuals that started LTBI therapy in 2010–2014 (Chi-squared 1216.6, df=1, p<0.001); ##: proportion of TST+ only versus TST+/IGRA individuals that completed LTBI therapy in 2010–2014 (Chi-squared 737.1, df=1, p<0.001); ¶¶: proportion of TST+ only individuals who started LTBI therapy versus TST+/IGRA individuals who started LTBI therapy, who completed LTBI therapy in 2010–2014 (Chi-squared 4.42, df=1, p =0.04).