Rutherford AI, et al. - Experts aimed to compare the incidence of serious infection (SI) across biologic drugs used to treat rheumatoid arthritis (RA) using data from the British Society for Rheumatology Biologics Register for Rheumatoid Arthritis (BSRBR-RA). In the primary analysis, the rate of SI was seen to be lower with certolizumab pegol than etanercept but in several sensitivity analyses performed the result was no longer significant suggesting residual confounding could account for the observed difference. From the findings of this study, it would be wrong to conclude that there was a lower rate of SI with certolizumab pegol than other biologics. Nonetheless, authors did not note the risk to be significantly higher as had previously been suggested.

Methods

• Authors conducted BSRBR-RA which was a prospective observational cohort study.
• The patients with RA starting a new biologic were included in this analysis .
• SI was the primary outcome defined as an infectious event requiring admission to hospital, intravenous antibiotics or resulting in death.
• They calculated the event rates and compared across biologics using Cox proportional hazards with adjustment for potential confounders.
• The rate of infection by organ class and 30-day mortality after infection were the secondary outcomes.

Results

• As per data, 19,282 patients with 46,771 years of follow-up were included in this analysis.
• Findings suggested the incidence of SI to be 5.51 cases per 100 patient years for the entire cohort (95% CI 5.29 to 5.71).
• In the fully adjusted model, tocilizumab was seen to have a higher risk of SI (HR 1.22, 95% CI 1.02 to 1.47) and certolizumab pegol a lower risk of SI (HR 0.75, 95% CI 0.58 to 0.97) than etanercept.
• Results demonstrated the 30-day mortality after SI to be 10.4% (95% CI 9.2% to 11.6%).