ABO blood group and individual risk for thrombosis. The bottom line

Objective: The authors review data supporting an association between ABO bl ood group and the risk for thrombotic events. Physiological as well as path ophysiological mechanisms which may contribute to this association are crit ically discussed. Data Sources: The Medline database was searched for artic les pertaining to 'ABO blood group', 'thrombosis', 'von Willebrand factor', and 'factor VIII'. Results: Individuals with blood group A, B or AB are fo und more frequently in patients with thrombotic diseases than is expected f rom the blood group distribution in healthy controls, whereas individuals w ith blood group 0 are underrepresented. The association between blood group and thrombosis may be mediated through an association between AB0 blood gr oup and von Willebrand factor concentration, which in turn correlates with factor VIII:C concentration. Conclusion: The thrombophilic predisposition observed in blood group A, B o r AB individuals may be due to elevated FVIII:C levels, leading to an imbal ance of pro- and anticoagulatory factors in these individuals, Combined wit h additional risk factors such as e.g. hereditary thrombophilia due to fact or V Leiden, this could lead to an increased risk for thrombosis in non-0 b lood groups. Prospective studies could help to assess the clinical relevanc e.