Morbidity and mortality related to tuberculosis (tb) in British Columbia (BC), Canada

BACKGROUND: The epidemiology of tuberculosis (TB) related recurrence and mortality is not well characterized for British Columbia (BC) or Canada. The objectives of this thesis were: 1) to estimate the incidence of recurrence of TB and identify predictors associated with TB recurrence; to investigate the relative contribution of exogenous re-infection as a mechanism of recurrence; to characterize mortality among TB patients and to identify potentially modifiable risk factors for patients whose deaths were attributable to TB. METHODS: This study was conducted using population-based data maintained by the centralized provincial TB service (TB Control Division at BC Center for Disease Control). All TB cases recorded with this Division from 1990 to 2006 were reviewed. TB patients who developed recurrence and who died during the observation period were identified. Cox regression was performed to identify risk factors associated with recurrence and mortality. RESULTS: During the study period (1990 to 2006), over 5400 TB patients were registered with the provincial TB control program. The incidence of recurrence was 370 per 100,000 person-years (pys). Several factors such as foreign-birth, incomplete treatment, poor-compliance to treatment, place of initial diagnosis, HIV and drug abuse were significantly associated with TB recurrence. The relative contribution of re-infection was 8% and the incidence of reinfection was 19 per 100,000 PYs. There was an excess mortality among TB patients compared to the general BC population. 1069 TB patients died during 1990 to 2006 (29 per 1000 PYs). The cumulative mortality at the first 6 and 12 months were 8% and 10% respectively. Increasing age, Aboriginal ethnicity, miliary TB, HIV/AIDS, alcoholism, substance abuse, etc was significantly associated with all-cause mortality in multivariable analyses. Among these deaths, 109 (109/5408=2%) deaths were primarily caused by TB and another 177 (177/5408=3.3%) deaths were partially contributed by TB (one of the causes of death). Miliary TB, far advanced PTB and Aboriginal ethnicity were the strongest predictors of mortality related to TB. CONCLUSIONS: This study identified several important risk factors in a population-based TB cohort. Effective interventions targeting these high-risk populations are urgently required in order to prevent recurrence and mortality related to TB.Medicine, Faculty ofPopulation and Public Health (SPPH), School ofGraduat