Venous thrombosis of the upper extremity: effect of blood group and coagulation factor levels on risk

Venous thrombosis of the upper extremity is a rare form of thrombosis, accounting for around 4% of all venous thromboses, and for which only a few risk factors are known. This case-control study investigated the effect of coagulation factors on risk of venous thrombosis of the upper extremity. Patients with venous thrombosis of the arm and partner controls were selected from the Multiple Environmental and Genetic Assessment study, a large population-based case-control study. Participants with a malignancy were excluded. Odds ratios (OR) were estimated for elevated levels of factor II, VII, VIII, IX, X, XI, von Willebrand Factor (VWF), and fibrinogen, low levels of protein C, protein S, and antithrombin, and for blood group non-O. Substantially increased risks of venous thrombosis of the upper extremity were found for patients with high levels (above 90th percentile versus below) of factor VIII (OR: 4·2, 95% confidence interval (CI): 2·2–7·9), VWF (OR: 4·0, 95% CI: 2·1–7·8), fibrinogen (OR: 2·9, 95% CI, 1·5–5·7), and for blood group non-O compared to O (OR: 2·1, 95% CI, 1·3–3·6). The other factors were not associated with an increased risk. Elevated levels of several procoagulant factors are associated with a strongly increased risk of venous thrombosis of the upper extremity.