Use of disease-modifying anti-rheumatic or anti-tumour necrosis factor drugs and risk of hospitalized infection in ankylosing spondylitis.

To assess the risk of hospitalized infection among initiators of disease-modifying anti-rheumatic drugs (DMARDs) and/or anti-tumour necrosis factor (anti-TNF) agents in ankylosing spondylitis (AS). We studied AS patients, new users of anti-TNF drugs and/or DMARDs between 1 January 2001 and 31 December 2011. Cohort entry was defined as the date of first prescription of any of these drugs. We used Cox regression with three time-varying drug exposures: current use of DMARDs without biologics, current use of anti-TNF agents alone or in combination with DMARDs (anti-TNF ± DMARDs), and current non-use. Models were adjusted for baseline patient sociodemographic characteristics, comorbidity, outpatient visits and procedures, previous infection, non-steroidal anti-inflammatory drugs, and corticosteroids. Hospitalized infection was defined on the basis of hospitalization discharge diagnoses (primary or non-primary) coding for infection. The cohort included 747 AS patients, with a mean age of 51.1 years (sd 14.6), and 466 (62.4%) were men. During the median follow-up of 1.98 years, 57 hospitalized infections occurred, for an incidence rate of 2.9/100 person-years. The adjusted hazard ratio of infection (relative to unexposed) was 1.00 [95% confidence interval (CI) 0.47-2.11] for the anti-TNF ± DMARDs group and 0.96 (95% CI 0.45-2.04) for DMARDs alone. Use of healthcare, corticosteroids, and previous hospitalized infections were associated with infection. We found no clear evidence that the risk of hospitalized infection was linked to DMARD and/or anti-TNF drug use. Because of scarce published literature on infection risk in AS patients, our results have important implications for clinicians.