Discordance between ABO-Related VWF Reduction and Global Hemostasis in Healthy Greeks: Implications for Assay Selection and the Disease Modifier Role of Blood Group O.

ABO blood group influences plasma levels of von Willebrand factor (VWF) and factor VIII (FVIII), with non-O individuals having higher levels and increased thrombotic risk. The relationship between ABO group and global hemostasis has not been studied in Greece. This study aims to examine the association between ABO blood group and VWF/FVIII levels in healthy Greek adults, and to assess whether ABO-related differences affect global hemostasis by viscoelastic methods. It is a cross-sectional study of 179 healthy blood donors (86 group O, 93 non-O). VWF:Ag, VWF:GPIbM, and FVIII:C were measured. Platelet function was assessed by Platelet Function Analyzer-100 (Col/Epi), and global hemostasis by ROTEM EXTEM. Group O had significantly lower VWF:Ag, VWF:GPIbM, and FVIII than non-O (all p < 0.001). No differences were observed between groups in Platelet Function Analyzer-100 or any ROTEM parameter. Platelet count and fibrinogen, not VWF, drove ROTEM parameters. ABO blood group significantly affects VWF and FVIII levels, but global hemostasis remains uncompromised in healthy individuals. However, as group O has been reported to act as a disease modifier in patients with underlying hemostatic defects, these findings highlight that no single assay can safely capture clinical hemostatic risk, and ABO blood group should be interpreted in clinical context.