Subjects in the family-based sample were classified as AA or EA based on a Bayesian model-based clustering method as previously described28 using approximately 400 short tandem repeat markers and more than 5000 SNP markers from the Illumina Linkage IVb Marker Panel. The race and ethnicity of subjects in the replication sample were self-identified. The genetic backgrounds of nearly two-thirds of these subjects were also analyzed with the Bayesian approach using a set of 180 ancestry informative markers. One hundred nineteen subjects in the replication sample who self-reported their ethnicity as something other than AA or EA and lacked ancestry informative marker data were excluded from further analysis. This resulted in a final replication sample of 1921 subjects. The AA and EA population groups were treated as independent samples for all primary analyses.
