Incidence of Tuberculosis Among Reported AIDS Cases in Quebec from 1979 to 1996

Background: The impact of HIV infection on tuberculosis (TB) rates in Quebec has not been fully established. Because concurrent HIV infection is the single most important factor in TB reactivation, the authors used Quebec AIDS surveillance data to quantify the extent of TB among reported AIDS cases and to identify the characteristics of AIDS patients with TB.

Methods: The study population comprised people aged 15 years and over with AIDS diagnosed between Jan. 1, 1979, and Dec. 31, 1996, and reported by Mar. 13, 1997. Patients with TB (all forms) and those without TB were compared. Multivariate logistic regression analysis was used to examine the independent effect of each variable on the AIDS-TB cases. The authors also compared the number of AIDS-TB cases with the number of TB cases to estimate the effect of HIV infection on TB incidence.

Results: Of the 4684 people with AIDS reported in Quebec, 242 (5.2%) had active TB at some point during the course of their illness. During 1992-1995, 9.6% of the people with TB in Montreal, and 5.8% in the province of Quebec, also had HIV infection. Those with AIDS and TB were predominantly male (75.2%), manual workers (40.1%) and residents of Montreal (86.4%) and were born in an HIV-endemic country (63.8%). The multivariate analysis indicated that AIDS patients who were born in HIV-endemic countries in the Caribbean, sub-Saharan Africa or other developing regions were 21.8 times (95% confidence interval [CI] 19.5-28.5), 17.9 times (95% CI 12.7-27.1) and 4.9 times (95% CI 3.5-7.0) more likely to have TB than those born in Canada; manual workers and unemployed people with AIDS were 1.6 times (95% CI 1.3-2.0) and 2.0 times (95% CI 1.5-2.6) more likely to have TB than professional workers; and people who acquired HIV infection through heterosexual contact were 2.1 times (95% CI 1.6-3.1) more likely to have TB than men who acquired it through sexual contact with other men.

Interpretation: AIDS seems to contribute significantly to the number of TB cases. The results of this study reinforce the importance of offering HIV testing to people in high-risk groups, such as those born in a country where HIV and TB is endemic.