Background Some data suggest that rheumatoid arthritis (RA) is associated with an increased risk of venous thromboembolism (VTE). Prior studies have been relatively small and used a very limited set of covariates to adjust for potential confounding.
Objectives To examine the risk of VTE in patients with RA compared to non-RA subjects.
Methods We conducted a retrospective cohort study using health care utilization data collected by a large US commercial insurance plan. The RA cohort included adults with at least two diagnoses of RA and at least one prescription for a disease-modifying anti-rheumatic drug (DMARDs). Follow-up began with the first prescription for a DMARD, defined as the index date. Subjects who never had a diagnosis of RA were selected and matched to RA patients on age, sex, and index date with a 5:1 ratio. Patients with history of malignancy and VTE were excluded. The primary outcome was VTE, defined as the composite of deep vein thrombosis (DVT) or pulmonary embolism (PE), as a principal hospital discharge diagnosis. Incidence rates (IR) and rate ratios (RR) of VTE with 95% confidence intervals (CI) were calculated. Multivariable Cox proportional hazards models compared the risk of VTE events between RA and non-RA patients.
Results The study population included 22,143 RA and 88,572 non-RA patients with a mean (SD) age of 52 (12) years with 75% women. During a mean follow-up of 2 years, 1.2% of RA patients and 0.5% non-RA patients developed VTE. The IR for VTE among RA patients was 6.1 per 1,000 person-years, 2.4 times higher (95% CI: 2.1-2.8) than the rate of non-RA patients. The IRs for both DVT (RR, 2.2, 95% CI: 1.9-2.6) and PE (RR 2.7, 95% CI: 2.2-3.5) were higher in RA patients compared with non-RA subjects. After adjusting for known risk factors of VTE, a moderately elevated risk for VTE was noted in RA (hazard ratio 1.4, 95% CI: 1.1-1.7) compared to non-RA patients.
Conclusions Our results showed an increased risk of VTE, both DVT and PE, for RA patients compared with non-RA patients. The risk was attenuated but remained elevated after adjusting for known risk factors for VTE such as cardiovascular disease, surgery, hospitalization, and medications.
Disclosure of Interest S. Kim Grant/Research support from: Pfizer, Takeda, S. Schneeweiss Grant/Research support from: Pfizer, Consultant for: WHISCON, RTI Health Solutions, the Lewin Group, and HealthCore, J. Liu: None Declared, D. Solomon Grant/Research support from: Amgen, Abbot, and BMS
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