Introduction Venous thromboembolism (VTE) is a major cause of mortality contributing up to 25 000 deaths per year. There are no published studies that have linked the risk of VTE to endoscopic procedures. The current study was designed to assess whether endoscopic procedures increase the risk of venous thrombosis.
Methods A retrospective case-control study of cases of patients (pts) with VTE from the Trust's Haemophilia department database over a 3-year period from 1 January 2009 to 31 December 2011. Each case was age and sex matched to one control patient, who attended an outpatient appointment during the same period. The notes and endoscopy reports of cases and controls were reviewed to identify those patients, who had undergone endoscopy in the preceding 3 months of the VTE diagnosis. All adult patients were included in the study. Pts undergoing OGD, flexible sigmoidoscopy, colonoscopy and ERCP were included. Endoscopic US and bronchoscopy pts were excluded. Study sample size was calculated from a literature review of an approximate 2% occurrence of endoscopy in the population and our internal pilot study suggesting a 5% incidence of endoscopy in patients with VTE. With a 5% significance level and 80% power we calculated that 425 subjects per group were required to confirm a difference in endoscopy between pts with VTE and controls. The difference in occurrence of endoscopy between cases and controls was examined using the Mc Nemar test. The risk of VTE occurring following endoscopy was quantified using ORs.
Results 45/445 (10.1%) patients had endoscopy in the VTE group compared to controls (14/445, 3.2%; p<0.001) of which, 21 had OGD, 17 colonoscopy, one had ERCP and six Sigmoidoscopy. The number of pts in each endoscopy procedure category was insufficient to confirm whether the risk of VTE was dependent on the type of procedure performed. The OR for developing a VTE after an endoscopic procedure was 3.58 (95% CI 1.86 to 7.46).
Conclusion 10% of patients with confirmed VTE had an endoscopy in the preceding 3 months of the diagnosis compared to 3% in the control group (p<0.001). Pts undergoing endoscopy have a 3.6-fold increased risk of VTE compared to controls. Larger studies may highlight whether the type of endoscopic procedure or diagnosis may alter this risk.
Competing interests None declared.
Reference 1. Nice guidelines CG-92.
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