Rheumatoid arthritis, its treatments, and the risk of tuberculosis in Quebec, Canada

To determine the risk of tuberculosis (TB) among a cohort of patients with rheumatoid arthritis (RA) in Quebec and assess whether this risk is associated with exposure to nonbiologic disease-modifying antirheumatic drugs (DMARDs).

We studied a cohort of patients with RA identified from the Quebec provincial physician billing and hospitalization databases for 1980-2003. TB incidence rates were determined for the period 1992-2003 and compared with the general population, standardized for age and sex using the standardized incidence ratio (SIR). Conditional logistic regression was used in a nested case-control analysis to estimate the rate ratio (RR) of TB related to nonbiologic DMARD exposure during the year before the index date.

Of the 24,282 patients with RA in the cohort, 50 cases of TB were identified. The standardized incidence rate was 45.8 cases per 100,000 person-years compared with 4.2 cases per 100,000 person-years in the general population of Quebec (SIR 10.9, 95% confidence interval [95% CI] 7.9-15.0). The adjusted RR of TB was 2.4 (95% CI 1.1-5.4) with corticosteroid use and 3.0 (95% CI 1.6-5.8) with nonbiologic DMARD use.

The age- and sex-standardized incidence rate of TB in RA patients is 10 times that of the general population. At least some of this risk may be related to nonbiologic DMARD and corticosteroid therapies. Our data support the role of TB screening before initiation of any immunosuppressive therapy.