The association between ankylosing spondylitis and the risk of venous thromboembolism: a meta-analysis

Background Autoimmune diseases are frequently associated with an increased risk of venous thromboembolism (VTE). However, the relationship between ankylosing spondylitis (AS) and VTE remains unclear. This meta-analysis was conducted to evaluate the association between AS and VTE risk, with the aim of providing evidence-based insights to guide clinical practice. Method We searched PubMed, Embase, the Cochrane Library, and Web of Science for studies published from database inception until June 2025 that compared VTE risk in patients with AS. Two researchers independently screened the literature based on predefined inclusion and exclusion criteria. The risk of bias in included studies was assessed using the Risk of Bias in Non-randomized Studies of Interventions (ROBINS-I) tool. Adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) were pooled to estimate effect sizes. Subgroup analyses were performed according to the type of thrombosis event. Sensitivity analysis was conducted by sequentially excluding each study. Publication bias was preliminarily assessed using funnel plots. The overall quality of evidence was evaluated using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) framework. All analyses were performed using RevMan 5.3 software. The study protocol was registered retrospectively in PROSPERO (Registration number: CRD420251107387). Results Six studies involving 601,585 patients were included. The meta-analysis indicated that AS was associated with a significantly higher risk of VTE (HR = 1.47, 95%CI(1.22,1.77), P < 0.0001; evidence quality: Very low). Subgroup analyses revealed that AS was significantly associated with an increased risk of overall VTE, deep vein thrombosis (DVT), and pulmonary embolism (PE) (VTE: HR = 1.57, 95%CI(1.26, 1.96), P < 0.0001; DVT: HR = 1.62, 95%CI(1.16, 2.26), P = 0.005; PE: HR = 1.24, 95%CI(1.06, 1.45), P = 0.008). Conclusion Current evidence indicates that AS may elevate the risk of VTE. Further mechanistic studies are needed to better interpret these findings derived from observational data. Systematic Review Registration https://www.crd.york.ac.uk/PROSPERO/ , identifier CRD420251107387.