• Huifang Liang, Raghava Danwada, Dianlin Guo, Jeffrey R Curtis, Ryan D Kilpatrick, Barbara Hendrickson, and Syed S Islam.
• Global Epidemiology, Pharmacovigilance and Patient Safety, AbbVie Inc, North Chicago, Illinois, USA.
• RMD Open. 2019 Jan 1; 5 (2): e001013.

ObjectivesTo assess incidence rates (IRs) of VTE in patients with rheumatoid arthritis (RA) on different DMARDs and DMARD switchers.MethodsAdults with RA on a DMARD between 2007 and 2017 were studied in a US claims database. Conventional synthetic DMARD (csDMARD) users, first biologic/targeted synthetic DMARD (b/tsDMARD) users and b/tsDMARD switchers (from a b/tsDMARD to another b/tsDMARD) were followed for inpatient VTE (pulmonary embolism (PE)/deep vein thrombosis (DVT)). Crude and adjusted IR and 95% CIs of VTE were estimated. HRs for VTE were estimated via Cox regression. VTE risk was also evaluated by number of switches between b/tsDMARDs and in patients without a VTE history.ResultsThe age and sex standardised IR (95% CI) of VTE (per 100 person-years) was 0.86 (0.70 to 1.03), 0.60 (0.52 to 0.68) and 0.58 (0.51 to 0.65) for b/tsDMARD switchers, first b/tsDMARD users and csDMARD users, respectively. After adjustment, b/tsDMARD switchers had an increased risk of VTE, compared with csDMARD users, HRadj (95% CI) being 1.36 (1.16 to 1.58), 1.36 (1.13 to 1.63) and 1.47 (1.18 to 1.83) for VTE, DVT and PE, respectively. Compared with first b/tsDMARD users, the HRadj (95% CI) for VTE was 1.35 (1.15 to 1.60) for first b/tsDMARD switchers and 1.48 (1.19 to 1.85) for second b/tsDMARD switchers.ConclusionsIn RA, b/tsDMARD switchers have a higher VTE risk compared with csDMARD users and first b/tsDMARD users. Switching b/tsDMARDs may be a proxy for higher disease severity or poorly controlled RA and an important confounder to consider in obtaining unbiased estimates of VTE risk in observational RA safety studies.© Author(s) (or their employer(s)) 2019. Re-use permitted under CC BY. Published by BMJ.

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