Effect of GPVI genotype on platelet GPVI expression. The total level of GPVI in platelets is compared between donors homozygous for the major haplotype (aa; n = 70), heterozygous donors (ab; n = 51), and donors homozygous for the minor haplotype (bb; n = 11). The mean level of each group is indicated by a horizontal bar. The calculated mean ± SD for each group is as follows: aa, 6.98 ± 2.45; ab, 7.14 ± 2.99; and bb, 7.37 ± 3.06. The differences between mean levels of any pair were not statistically significant, as follows: aa versus ab, P = .749; aa versus bb, P = .586; and ab versus bb, P = .812.