Comparative risk of incident venous thromboembolism in patients with inflammatory bowel disease initiating tumour necrosis factor- inhibitors or nonbiologic agents: a cohort study

BACKGROUND: Inflammatory bowel disease (IBD) increases the risk of venous thromboembolism (VTE) by 2 to 3 times. We compared the reduction in risk of incident VTE associated with use of tumour necrosis factor- (TNF-) inhibitors versus nonbiologic immunomodulatory agents in patients with IBD. METHODS: This observational cohort study used data from public (Medicaid, 2000-2010; Medicare, 2007-2013) and private (Optum Clinformatics, 2004-2013) health insurance programs in the United States. We included a total of 21 671 patients who had IBD without a prior diagnosis of cancer or VTE. The exposure of interest was treatment initiation with TNF- inhibitor or nonbiologic (azathioprine, mercaptopurine, methotrexate, cyclosporine). The outcome of interest was admission to hospital with VTE as the principal diagnosis. We used Cox proportional hazard regression models to estimate hazard ratios (HRs) separately for each database after risk adjustment for more than 50 covariables using propensity score fine stratification. We used inverse variance meta-analytic methods to pool the adjusted HRs across the 3 databases. RESULTS: We included a total of 5173 patients who started TNF- inhibitor therapy (1439 in the Medicaid database, 1480 in Medicare and 2254 in Optum Clinformatics) and 16 498 who initiated a nonbiologic agent (5041 in Medicaid, 5166 in Medicare, 6291 in Optum Clinformatics). The adjusted pooled HR for VTE risk with TNF- inhibitor versus a nonbiologic agent was 0.78 (95% confidence interval [CI] 0.60 to 1.02). The HR was lower in patients with Crohn disease (pooled HR 0.62, 95% CI 0.44 to 0.86) and younger patients (18-44 yr; pooled HR 0.55, 95% CI 0.34 to 0.87). INTERPRETATION: We did not find a statistically significant association between risk of VTE and use of TNF- inhibitors, relative to nonbiologics, in patients with IBD overall. However, an association was evident for patients younger than 45 years and those with Crohn disease.