Effect of ABO blood group on the collagen-binding assay for von Willebrand factor.

von Willebrand disease (VWD) is the most common congenital bleeding disorder and is caused by a quantitative or qualitative abnormality of von Willebrand factor (VWF). Ristocetin cofactor (RCoF) assay is used to evaluate VWF activity, but it does not assess collagen-binding activity. Normal values of RCoF and VWF antigen vary with ABO blood group type. The collagen-binding assay (CBA) measures VWF activity; however, its relationship with ABO blood group has not been completely explored. We performed CBA on plasma samples from 131 healthy volunteers to determine if CBA values correlated with blood type. Individuals with blood group O had a mean CBA value of 94 +/- 28%, which was significantly different from the mean of 117 +/- 33% in persons with non-O blood groups (P = 0.0001). Thus, CBA values appear to correlate with ABO blood type in a manner similar to RCoF.