VWF activity to antigen ratios by race and D1472H status. (A) VWF:RCo/VWF:Ag ratios for African American (AA) and Caucasian (CA) subjects with or without the D1472H polymorphism. (B) VWF:CB/VWF:Ag ratios for African American and Caucasian subjects with or without the D1472H polymorphism. The mean value for each group is listed at the top of the graph. Error bars represent ± 1 SD.