Many studies  have shown that in non-O blood group individuals, Factor VIII - von willebrands factor (vWF) complex levels in plasma were in [approximately equal to]25% more than compared to O blood group individuals.
Functional effects of the ABO locus polymorphism on plasma levels of von willebrand factor, factor VIII, and activated partial thromboplastin time.
The effect of ABO blood group on the diagnosis of von willebrand disease.
ABO blood group determines plasma von willebrand factor levels: A biologic function after all?
Brown et al., "Is it congenital or acquired von Willebrands disease?," Haemophilia, vol.
Further workup with coagulation studies showed decreased factor VIII, vWF antigen, and vWF: ristocetin cofactor assay, and negative Bethesda assay, indicating acquired von Willebrand disease.
Acquired von Willebrand disease (AvWD) is a rare bleeding disorder [1, 2].
His factor VIII activity was 12%, and von Willebrand factor antigen was 4%.
Collagen binding assay for von Willebrand factor (VWF:CBA): detection of von Willebrands disease (VWD), and discrimination of VWD subtypes, depends on collagen source.
The function of von Willebrand factor (VWF)  is dependent on the presence of high molecular weight multimers (HMWM).
Types 2A and 2B von Willebrand disease (VWD), both lacking HMWM, are characterized by excessive mucosal bleeding.
Full-length von Willebrand factor (VWF) gene sequencing was performed for all index cases and healthy controls, including all intron- exon boundaries (14).