VWF and vascular disorder: It has been reported that non-O blood groups (ie, blood groups A, B and AB) are associated with significantly higher risk of VTE and cardiovascular disease, including myocardial infarction, peripheral vascular disease and cerebrovascular stroke.4–8 This could, in part, be explained by blood group O patients having 25%–30% lower levels of circulating Factor VIII (FVIII) and von Willebrand factor (VWF).15 However, Dentali et al6 demonstrated that non-O patients were at an increased risk of VTE even after adjustment for different levels of FVIII/VWF.