Fig. 3. Allele and genotype frequencies by age at first coronary artery bypass grafting (CABG) tertile. The CABG population was stratified into equal tertiles by age at first CABG (first tertile = age 54 years and younger; second tertile = age 55–65 years, inclusive; third tertile = age 66 years and older). Bars denote relative allele and genotype frequencies in each tertile as indicated. (A and B ) Tissue factor (TF) allele and genotype frequency by age at first CABG tertile, respectively. Statistically significant differences across the three age groups were demonstrated by chi-square test with linear-by-linear association (P = 0.007 and 0.008, respectively). (C and D ) Glycoprotein Ib-α variable number of tandem repeat allele and genotype frequency by age at first CABG tertile, respectively. Statistically significant differences across the three age groups were demonstrated by chi-square test with linear-by-linear association (P = 0.005 and 0.004, respectively). Del = deletion allele; Ins = insertion allele. Alleles B, C, and D are defined in the text.