F11 and Venous thrombosis: In fact, Meijers JCM et al. [6] reported an increased risk of developing venous thrombosis in subjects with increased plasma FXI levels, with an adjusted OR of 2.2 (95% CI, 1.5 to 3.2) similar to that observed in our study (OR 2.4, 95% CI 1.3 to 5.5).