VWF:RCo/VWF:Ag ratio in African American (AA) controls by D1472H allele status. VWF:RCo/VWF:Ag ratios are shown for African American subjects homozygous for the 1472H allele (1472 HH), heterozygotes (1472 DH), and those homozygous for the 1472D allele (1472DD). The mean value for each group is listed at the top of the graph. Error bars represent ± 1 SD.