THU0667 OVERALL INFECTION RISK IN PATIENTS WITH RHEUMATOID ARTHRITIS RECEIVING ABATACEPT, RITUXIMAB AND TOCILIZUMAB. AN OBSERVATIONAL COHORT STUDY

Abstract

Background Most infections in patients with rheumatoid arthritis (RA) are treated in primary care with a prescription of antibiotics. Only a small fraction requires hospitalization. Existing studies of infection risk in patients with RA, who receive non-tumor-necrosis-factor-inhibitor biologic (non-TNFi) therapy, however, have focused primarily on hospitalized infections.(1) Objectives In Danish RA patients treated in routine care with the three non-TNFi abatacept, rituximab and tocilizumab 1) to compare adjusted incidence rates (IR) of infections overall, and 2) to estimate the relative risk (RR) of infections across the drugs during the first year of non-TNFi treatment. Methods We conducted an observational cohort study including all RA patients in DANBIO who started a non-TNFi treatment between January 2010 and December 2017. Clinical characteristics at baseline were described. We defined infections as either a prescription of antibiotics or a hospitalization due to infection. Baseline comorbidities, antibiotic prescriptions and hospitalized infections were identified through linkage to national registries. We calculated IRs of infections per 100 person-years (age and gender adjusted) and rate ratios (as estimates of RRs, adjusted for additional covariates) during the first year of treatment (Poisson regression). Results We identified 3,696 treatment series of non-TNFi (abatacept 1,115/rituximab 1,017/tocilizumab 1,564). Patients receiving rituximab tended to be older, had longer disease duration and more previous malignancies. During the first year of treatment, 1,747 infections were identified. Age and gender adjusted IRs per 100 person years were (abatacept/rituximab/tocilizumab): 76.1(69.3; 83.6)/87.3(79.3; 96.1)/77.4(71.4; 83.9). Adjusted RRs (Table) were 0.88(0.76; 1.02) for abatacept and 0.87(0.75; 1.00) for tocilizumab compared to rituximab. For abatacept vs. tocilizumab it was 1.02 (0.89; 1.16). Conclusion In patients with RA receiving treatment with abatacept, rituximab or tocilizumab in routine care, rituximab had the highest risk of infection during first year of treatment. However, this finding should be interpreted with caution due to differences in baseline characteristics across drugs and potential residual confounding.