Background Infection is a complication of biologic therapy in RA.
Objectives To describe the incidence and pattern of serious infection within the British Society for Rheumatology Biologics Register (BSRBR-RA) by drug.
Methods The BSRBR-RA is a prospective observational study designed to evaluate the safety of biologics. Adverse events are coded using MedDRA defintitions. This analysis included patients with RA starting a biologic. They were considered at risk from their start date until 3 half-lives after stopping their biologic, death, first serious infection, or completion of three years of therapy, whichever came first. Event rates were compared across biologics using Cox proportional hazards with adjustment for age, gender, disease severity and duration, smoking, seropositivity, polypharmacy and baseline steroid usage.
Results 19,282 patients were included in the analysis with combined follow-up time of 46,771 years. At baseline the mean age was 57 years, 76% female, mean disease duration 12.3 years and mean DAS28 6.1. 22% were current smokers and 64% had a positive rheumatoid factor. The incidence of serious infection for each biologic and hazard ratios for serious infections including by subclass are tabulated.
A sensitivity analysis limiting to 1st biologic exposure only did not significantly alter the estimates. A second sensitivity analysis limiting to new starters from 2010 found certolizumab still had a lower point estimate but findings were no longer significant (HR 0.79, CI 0.54–1.16).
Conclusions Although the incidence of serious infection was lowest with certolizumab it is difficult to draw strong conclusions about comparative safety from observational studies due to channelling bias and unmeasured confounding.
Rituximab and tocilizumab both had higher unadjusted rates of infection but in the adjusted model the rate was no different suggesting that patient factors as opposed to the drug itself were responsible for the observed difference.
Disclosure of Interest A. Rutherford: None declared, S. Subesinghe: None declared, R. Byng-Maddick: None declared, K. Hyrich Grant/research support from: Pfizer, Speakers bureau: Abbvie, J. Galloway Consultant for: Roche, BMS, UCB, Pfizer