Risk of venous thromboembolism in patients with rheumatoid arthritis: initiating disease-modifying antirheumatic drugs.

OBJECTIVES: Recent research suggests that rheumatoid arthritis increases the risk of venous thromboembolism. This study compared the risk of venous thromboembolism in patients with newly diagnosed rheumatoid arthritis initiating a biologic disease-modifying antirheumatic drug (DMARD) with those initiating methotrexate or a nonbiologic DMARD.

METHODS: We conducted a population-based cohort study using US insurance claims data (2001-2012). Three mutually exclusive, hierarchical DMARD groups were used: (1) a biologic DMARD with and without nonbiologic DMARDs; (2) methotrexate without a biologic DMARD; or (3) nonbiologic DMARDs without a biologic DMARD or methotrexate. We calculated the incidence rates of venous thromboembolism. Cox proportional hazard models stratified by propensity score (PS) deciles after asymmetric PS trimming were used for 3 pairwise comparisons, controlling for potential confounders at baseline.

RESULTS: We identified 29,481 patients with rheumatoid arthritis with 39,647 treatment episodes. From the pairwise comparison after asymmetric PS trimming, the incidence rate of hospitalization for venous thromboembolism per 1000 person-years was 5.5 in biologic DMARD initiators versus 4.4 in nonbiologic DMARD initiators and 4.8 in biologic DMARD initiators versus 3.5 in methotrexate initiators. The PS decile-stratified hazard ratio of venous thromboembolism associated with biologic DMARDs was 1.83 (95% confidence interval [CI], 0.91-3.66) versus nonbiologic DMARDs and 1.39 (95% CI, 0.73-2.63) versus methotrexate. The hazard ratio of venous thromboembolism in biologic DMARD initiators was the highest in the first 180 days versus nonbiologic DMARD initiators (2.48; 95% CI, 1.14-5.39) or methotrexate initiators (1.80; 95% CI, 0.90-3.62).

CONCLUSIONS: The absolute risk for venous thromboembolism was low in patients with newly diagnosed rheumatoid arthritis. Initiation of a biologic DMARD seems to be associated with an increased short-term risk of hospitalization for venous thromboembolism compared with initiation of a nonbiologic DMARD or methotrexate.