Opportunistic infections in rheumatoid arthritis patients exposed to biologic therapy: results from the British Society for Rheumatology Biologics Register for Rheumatoid Arthritis.

Objectives: This analysis set out to estimate the risk of opportunistic infection (OI) among patients with RA by biologic class.

Methods: The British Society for Rheumatology Biologics Register for Rheumatoid Arthritis is a prospective observational cohort study established to evaluate safety of biologic therapies. The population included adults commencing biologic therapy for RA. The primary outcome was any serious OI excluding tuberculosis (TB). Event rates were compared across biologic classes using Cox proportional hazards with adjustment for potential confounders identified a priori. Analysis of the incidence of TB was performed separately.

Results: In total, 19 282 patients with 106 347 years of follow-up were studied; 142 non-TB OI were identified at a rate of 134 cases/100 000 patient years (pyrs). The overall incidence of OI was not significantly different between the different drug classes; however, the rate of Pneumocystis infection was significantly higher with rituximab than with anti-TNF therapy (adjusted hazard ratio = 3.2, 95% CI: 1.4, 7.5). The rate of TB fell dramatically over the study period (783 cases/100 000 pyrs in 2002 to 38 cases/100 000 pyrs in 2015). The incidence of TB was significantly lower among rituximab users than anti-TNF users, with 12 cases/100 000 pyrs compared with 65 cases/100 000 pyrs.

Conclusions: The overall rate of OI was not significantly different between drug classes; however, a subtle difference in the pattern of OI was seen between the cohorts. Patient factors such as age, gender and comorbidity were the most important predictors of OI.