The ABO Blood System and Associated Implications for Hemostasis and Thrombosis

The relationship between non-O blood groups and thromboembolic events has been suggested by several studies, although the exact underlying mechanisms are not fully elucidated. However, the correlation between ABO blood groups with the opposite pole of hemostasis, hemorrhage, has been investigated less thoroughly. Non-O blood groups confer an overall increased risk of single, recurrent, and provoked thromboembolic episodes. On the other hand, blood group O has been associated with more severe bleeding events and less favorable manifestations in individuals with hemorrhagic disorders. Therefore, ABO blood group screening may have a role in both thrombotic and hemorrhagic risk assessment and could potentially be added to available clinical prediction systems. This strong belief is supported by the ongoing research. Nevertheless, up to date, the majority of studies represent important heterogeneity, and given the frequency of non-O blood groups, a natural reluctance to incorporate blood groups in risk assessment models arises. Therefore, a more targeted approach should be considered to provide safe outcomes. The in vitro estimation of the thrombotic and hemorrhagic profile of each blood group separately, the quantitative estimation of VWF, FVIII, and platelet function in several disease settings and in well-organized studies, could be useful to establish a clear relationship of ABO blood types with hemostatic and thrombotic disorders. This may ensure a safe approach to categorizing a patient's risk, managing treatment, and influencing prognosis.