ABO blood group also influences the von Willebrand factor (VWF) antigen level in heterozygous carriers of VWF null alleles, type 2N mutation Arg854Gln, and the missense mutation Cys2362Phe

The levels of von Willebrand factor (VWF) in plasma are influenced by several variables, such as age, blood group, pregnancy, hormones, and smoking. The VWF levels may vary greatly on repeated laboratory testing in the same subject.[1][1] About 60% of the variation in plasma VWF is caused by genetic