Abatacept initiation in rheumatoid arthritis and the risk of serious infection: A population-based cohort study.

OBJECTIVE: To assess whether abatacept as initial biologic disease-modifying antirheumatic drug (DMARD) in the treatment of rheumatoid arthritis is associated with an increased risk of serious infections, including bone and joint, gastrointestinal, respiratory tract, skin and soft tissue, and urinary tract, when compared with other biologic DMARDs. METHODS: We performed a population-based cohort study among patients newly-treated with biologic DMARDs within the US-based Truven MarketScan® population and Supplemental US Medicare from 2007 to 2014. Cox proportional hazards models were used to estimate adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) of serious infections requiring hospitalisation associated with initiation of abatacept, compared with initiation of other bDMARDs, after controlling for age and deciles of the propensity score. RESULTS: The cohort included 5,752 patients who initiated abatacept and 78,556 who initiated another biologic DMARD, of whom 193 and 1531 had a serious infection during follow-up (crude incidence rate 4.45 per 100 person-years and 3.62 per 100 person-years, respectively). Compared with other biologic DMARDs, the use of abatacept was not associated with an increased incidence of serious infections overall (HR 1.04, 95% CI 0.89-1.21). The risk did not vary by duration of use (<1 year: HR 1.03, 95% CI 0.87-1.22; >1 year: HR 1.08, 95% CI 0.77-1.52). In addition, the risk was not increased for the site-specific infections. CONCLUSION: The use of abatacept as first biologic DMARD in the treatment of rheumatoid arthritis was not associated with different risks of serious infections compared with other biologic DMARDs.