COMPARATIVE INCIDENCE OF TUBERCULOSIS IN CANADA: THE PAST, PRESENT AND FUTURE
Canada and the United States (US) are both high income, low tuberculosis (TB) incidence countries with similar TB control programs, yet an explicit comparison of TB incidence over time is lacking. Objective one explored the impact of TB and other disease case definition change, and methods to control for the change via a general literature search. Underreporting/increases in reported cases and differences in sensitivity and specificity measures were among others noted to arise from changes in case definition. For appropriate comparisons within and between populations, consistent ascertainment criteria of cases should be adopted. Objective 2 explored and compared TB incidence rates in Canada and the US from 1953-2015. TB rate from 1953-2015 was retrieved for both countries. Joinpoint and direct standardization were performed. Canada’s TB rates/100,000 were higher from 1953-1974. Canada’s average annual percent change in rate from 1975-2015 was -2.9% compared to the US -4.1%. Case definition change, HIV+/TB co-infection, and Foreign-born (FB) TB were the main contributors to the differences. Objective three compared the rate of TB decline in subpopulations. TB cases and population by ethnicity from 2001-2011, and the percent of HIV+/TB co-infection cases from 1997-2012 were retrieved for Canada and the US. Segmented and decomposition analysis was performed. FB and Indigenous TB rate declined by -3.7% and -6.3% in the US and by -1.7% and -4.5% in Canada. Changes in age-specific rates declined overall rates in Canada by 80.1% and the US at 66.7%. Overall, the percentage of HIV+/TB cases declined more rapidly in the US than in Canada. After adjusting for age, FB and Indigenous populations, rates decline more in the US than in Canada. Objective four forecasted and then compared year-over-year TB rates between Canada and US from 2017-2035. TB rate from 1975-2016 and rates by ethnicity from 1993-2016 were retrieved for both countries. Autoregressive integrated moving average and multivariate vector autoregression models were performed. The forecasted models showed a gradually decreasing trend from 2017-2035, reaching a rate of 2.2 for Canada and 1.3 for the US by 2035. The prediction suggests that achieving 2035 WHO set target could be a challenge for both countries.
Tuberculosis, Joinpoint, Incidence Rate, Trends, Definition Change, Tuberculosis Epidemiology
Doctor of Philosophy (Ph.D.)
School of Public Health