SAN DIEGO, CA—Initiation of biologic disease-modifying antirhuematic drugs was significantly associated with a 2.5-times elevated risk of venous thromboembolism (VTE) in the first 180 days, according to study results presented at the 2013 ACR/ARHP Annual Meeting.

Seoyoung C. Kim, MD, MSCE, and colleagues, of the Division of Pharmacoepidemiology and Pharmacoeconomics, Division of Rheumatology, Allergy, and Immunology, Brigham and Women’s Hospital, Boston, MA, conducted a population-based cohort study to compare the risk of VTE in rheumatoid arthritis (RA) patients initiating treatment with biologic disease-modifying antirheumatic drugs (bDMARD), methotrexate, or non-biologic DMARD (nbDMARD).

The study combined three U.S. commercial insurance claims databases (2001—2012) that identified adult patients (n=29,481) with a new diagnosis of RA based on >2 RA diagnoses that were >7 days apart with a baseline period free of RA diagnosis or DMARD use for >1 year. Patients with a history of VTE, malignancy and use of anticoagulants at baseline were excluded.

The three drug regimens were classified as the following: (1) a biologic DMARD with or without nbDMARDs, (2) MTX without a biologic DMARD, or (3) nbDMARDs without a biologic DMARD or MTX. Incidence rates (IR) of VTE identified by a previously validated algorithm with inpatient diagnosis codes (PPV 75—90%).

Of the total patients, 39,647 treatment episodes were identified. The crude IR of VTE per 1,000 person-years was higher in the bDMARDs group (5.53, 95% CI 3.67—8.32) vs. nbDMARDS (4.43 95% CI 3.13—6.26) and methotrexate. The hazard ratio (HR) of VTE associated with initiation of bDMARDs was 1.83 (95% CI 0.92–3.63) compared to nbDMARDs and 1.39 (95% CI 0.73-2.64) compared to methotrexate.

The HR of VTE associated with initiation of methotrexate vs. nbDMARDs was 0.78 (95% CI 0.50—1.21). In a sensitivity analysis limiting the follow-up up to 180 days, bDMARDs was associated with a significantly increased risk (HR 2.48, 95% CI 1.14—5.40). In the PS-matched analyses, the HR was 1.34 (95% CI 0.65—2.75) in bDMARDs vs. nbDMARDs and 1.73 (95% CI 0.90—3.32) in bDMARDs vs. methotrexate.

“Initiating a bDMARD was associated with a likely increase, but not statistically significant, in the risk of incident VTE compared to those initiating methotrexate or nbDMARDs, albeit low absolute risks of VTE,” concluded Dr. Kim.