BERLIN– Rheumatoid arthritis patients face a moderately elevated risk of venous thromboembolism that continues unabated for many years, according to findings from two large studies presented at the European Congress of Rheumatology.
Dr. Seoyoung C. Kim offered a retrospective cohort study involving 22,143 patients with rheumatoid arthritis (RA) and 88,572 age- and sex-matched controls. None of the subjects had a baseline history of malignancy or venous thromboembolism (VTE). The data came from a large U.S. commercial insurance plan.
During a mean follow-up of 2 years (starting when the RA patients received their first prescription for a disease-modifying antirheumatic drug), deep vein thrombosis or pulmonary embolism occurred in 1.2% of RA patients and 0.5% of controls. The incidence among RA patients was 6.1 cases per 1,000 person-years, a rate 2.4-fold greater than in controls. The pulmonary embolism rate was 2.7 times higher than in controls, whereas the deep vein thrombosis rate was 2.2-fold higher, according to Dr. Kim of Brigham and Women’s Hospital, Boston, where she is a rheumatologist.
After adjustment for known risk factors for VTE, including surgery, hospitalization, and cardiovascular disease, the VTE risk associated with having RA remained moderately elevated, with a 40% increase compared with controls.
The mechanism underlying this increased risk is believed to hinge upon the systemic inflammation that is a central feature of RA. This inflammation is thought to predispose to thrombus formation, up-regulation of procoagulants, down-regulation of anticoagulants, and suppression of fibrinolysis, Dr. Kim noted.
Dr. Marie Holmqvist presented a prospective population-based cohort study including 8,077 patients who were newly diagnosed with RA during 1997-2009, as well as 203,329 controls.
In all, 84 RA patients were diagnosed with a pulmonary embolism during 43,178 person-years of prospective follow-up. That translated to an incidence of 1.9 cases per 1,000 person-years, compared with 1.1 cases per 1,000 person-years among controls.
The increased risk of pulmonary embolism was evident 1 year after diagnosis of RA and remained unchanged thereafter. In the period 1-4 years after diagnosis of RA, the RA group had a 1.8-fold greater risk of pulmonary embolism than did controls drawn from the general population. During years 5-9, the risk was increased 2.0-fold, and in years 10-15 the risk of pulmonary embolism in RA patients was 1.9-fold greater than in controls, although only a small number of subjects were followed that long.
Control subjects who were hospitalized for any reason had a 5.4-fold increased risk of pulmonary embolism for the next year, compared with nonhospitalized controls. The risk of pulmonary embolism in hospitalized RA patients was elevated for the next year to the same extent as in hospitalized controls. In other words, having RA didn’t pile on additional risk beyond hospitalization itself, according to Dr. Holmqvist of the Karolinska Institute, Stockholm.
Dr. Holmqvist and Dr. Kim reported having no financial conflicts. Neither study had commercial sponsorship.