Greater Need for FVIII Replacement in Patients of Type Non-O Blood Groups with Moderate Hemophilia A

Abstract 4390

Hemophilia A is a bleeding disorder of variable expressivity caused by mutations in clotting factor 8 gene located on Xq28 chromosome. In Brazil, treatment of such patients consists of replacement therapy with FVIII concentrate derived from human plasma, which is administered either to control an episode of hemorrhage or prophylactically in order to prevent bleeding and its consequences, such as arthropathy. Recent studies have demonstrated that the half-life of FVIII administered to patients of the type O blood group with severe hemophilia A is shorter than that in patients of Type non-O groups. A likely explanation for this fact would be the greater plasma concentration of von Willebrand factor (vWF) in individuals with type non-O blood. In this study, was investigated the association between the blood group and the annual consumption of FVIII concentrate (UI/Kg/year) in the last three years among 99 patients (68 with moderate and 31 with mild hemophilia A) treated at the two blood centers in Brazil (Hemocentro do Pará and Hemocentro/UNICAMP). Most cases were treated for episodes of hemorrhage. Determinations of antigen levels of von Willebrand factor (vWF:Ag), activity of ristocetin cofactor (vWF:RiCof) and FVIII clotting activity (FVIII:C) were performed to investigate the correlation between these variables and immunophenotypes of the ABO blood system. The Mann-Whitney test was used for the comparison of FVIII consumption (UI/Kg/year) between O type and non-O type hemophiliacs, with the level of significance set to 5% (p<0.05). Unexpectedly, significantly greater FVIII consumption was found among patients of the non-O type group (p=0.017). In the evaluation of patients with moderate hemophilia A, plasma levels of vWF:RiCof were significantly higher in non-O type patients in comparison to those with type O blood (p=0.045). No significant differences were found between blood groups in the evaluation of patients with mild hemophilia A. The present findings lead one to conclude that the higher level of plasma vWF:RiCof (which could exert an influence on the increased half-life of FVIII) in patients of the non-O type group with moderate hemophilia A was not enough to impede the need for greater FVIII replacement and lessen the frequency of bleeding in this group. The authors hypothesize that other variables, such as mutations in moderate hemophilia A, affect the stability of the FVIII molecule, which has antigen A and B determinants in individuals of non-O type groups. Further studies involving a larger sample are needed to corroborate the findings of the present investigation.