The risk of venous thromboembolic events in patients with inflammatory bowel disease: a systematic review and meta-analysis

Background Inflammatory bowel disease (IBD), comprising Crohn's disease (CD) and ulcerative colitis (UC), is a chronic inflammatory disorder of the gastrointestinal tract that has been associated with increased risk of extraintestinal manifestations, amongst which is venous thromboembolism (VTE). We assessed the risk for VTE in patients with IBD through systematic review and meta-analysis. Methods A systematic search for English language studies was conducted in Medlin, Scopus, and the Cochrane Library of publications from database inception till August 10, 2020, to identify relevant studies reporting the risk of VTE in patients with IBD. The random-effects and fixed-effect models were used to estimate relative risks (RRs) with their respective 95% confidence intervals (CIs). The quality of the included studies was assessed using the Newcastle-Ottawa scale. Results Eleven observational studies were included in this meta-analysis, involving 3,175,012 patients with IBD and 920,144,253 controls without IBD. The overall RR for VTE in patients with I BD compared to non- IBD individuals was 2.03 (95%CI 1.72-2.39). An analysis of studies with larger population size demonstrated a lower risk for VTE (RR 1.77, 95%CI 1.48-2.13) among patients with IBD, whereas studies with a smaller population size yielded a greater risk for VTE (RR 2.67, 95%CI 1.97-2.93). After adjustment for smoking and body mass index, the RR for VTE was moderately increased (RR 2.65, 95%CI 1.51-4.65). Conclusions The present meta-analysis shows that IBD is linked to a 2-fold increased risk for VTE. Thus, primary prevention against VTE is of the utmost importance.