Clinical Outcomes of Venous Thromboembolism in Patients with Ankylosing Spondylitis vs. Other Immune-mediated Inflammatory Diseases: Insights from the RIETE Registry

Ankylosing spondylitis (AnkS) has been associated with an increased risk of venous thromboembolism (VTE). Data comparing VTE events in AnkS with other immune-mediated inflammatory diseases and non-inflammatory patients are lacking. This study aimed to compare clinical outcomes between VTE patients with AnkS, rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), inflammatory bowel disease (IBD), and patients without inflammatory disease. We analyzed 112,539 VTE patients enrolled in the RIETE registry. A Greedy Nearest Neighbor Matching approach was used to select a comparable non-inflammatory VTE cohort. Outcomes included recurrent VTE, mortality, and major bleeding at 1 year, and were compared using Cox regression or sub-hazard models. Among the inflammatory-disease cohort of 2,427 VTE patients (mean age ± standard deviation, 64.1 ± 16 years, 41.4% males), 6.4% had AnkS, 50.6% had RA, 10.8% had SLE, and 32.2% had IBD. The matched population without inflammatory disease comprised 7,800 VTE patients. The rate of recurrent VTE was 11.5%, all-cause mortality 5.1%, and major bleeding 1.9% in AnkS patients. Similar rates were observed in patients with RA, SLE, or IBD. Recurrent VTE was significantly higher in AnkS patients than in the non-inflammatory group (HR, 7.43, 95% CI, 2.28–24.23). AnkS patients who discontinued anticoagulation earlier than 1 year experienced higher adverse outcomes (a composite of mortality, major bleeding, recurrent VTE) compared with those who pursued extended therapy. VTE patients with AnkS have clinical outcomes comparable to other inflammatory diseases but a significantly increased risk of recurrent VTE compared with non-inflammatory patients, suggesting that extended anticoagulation strategies may be warranted.