Abstract
ABO blood group has been described to influence levels of von Willebrand factor (VWF), as well as factor VIII. Individuals carrying O allele have significant lower plasma levels of these factors. Indeed, recently non-O individuals have been described to have increased risk for both, arterial and venous thrombotic disease. VWF mediate platelet interaction with areas of damage blood vessel wall. Thus, it could be interesting to evaluate the possible influence of the ABO group in this interaction, particularly in situations in which low levels of VWF are close to those found in VW disease (such in O group). Cone and plate(let) analyzer (CPA) represent a simple and fast method, that allow the evaluation of platelet function (adhesion as well aggregation) in whole blood under shear conditions, closer to physiological conditions. In this method, no platelet agonists are needed and interaction with fibrinogen and VWF is particularly evaluated. The aim of the present study was to evaluate the influence of ABO group in platelet function using CPA. Samples from 15 male blood donors with no history of drug intake, were submitted to ABO serology and molecular analysis, VWF:Ag, FVIII dosages, and CPA analysis using Impact-R (Diamed - Switzerland), according to manufacturer’s instructions. ABO phenotypes were determined by agglutination test using monoclonal and polyclonal anti-A, B and AB antibodies (Asem-NPBI, São Paulo Brazil; DiaMed SA, Suisse; DiaMed Latino América, Brazil). H antigen was determined using anti-H lectin from Ulex europaeus (DiaMed Latino América, Brazil). ABO genotyping was performed by polymerase chain reaction (PCR) amplification of exons 6 and 7 of the ABO gene, followed by diagnostic restriction enzyme digestion. Factor VIII coagulant was measured by a one stage clothing method using a factor-VIII deficient substrate. VWF:Ag was measured by an enzyme linked immunosorbent assay (ELISA) using polyclonal antiserum (Dako, Denmark). Lyophilised commercial reference preparations of VWF:Ag, and FVIII, standardized against the World Health Organization standard, were used as the standards in this study. The age of the donors ranged from 27–65 years (median = 42 years). The donors were distributed according to ABO groups: 5 = OO; 5 = AB; 5 = AO. Median levels of factor VIII, according to blood group were: OO= 79% (70–142%); AO= 87% (80–140%); AB= 112% (98–200%). Median levels of VWF, according to blood group were: OO= 79% (50–99%); AO= 82% (73–120%); AB= 169% (92–250%). CPA analysis presented the following results: median AS in μm2 (average size) - OO= 24 (23–42); AO= 33 (24–42); AB= 23 (21–24) - median SC in % (surface coverage) - OO= 7.1 (4–13); AO= 8 (5–8); AB= 6.9 (4.8–8). No significant differences using Wilcoxon’s rank sum test were found among groups, when platelet function was analyzed. In conclusion, our results suggest that, although O allele carriers present lower levels of both factor VIII and VWF, the use of platelet function analysis does not seem to predict the risk for bleeding or thrombosis, according to individual ABO blood group.
von Willebrand factor: evidence for variable clearance in vivo according to Y/C1584 phenotype and ABO blood group
