We conducted two GWA studies, one in a sample of individuals of EA and the second in a sample of individuals of AA. In order to account for possible genetic background differences, we: 1) considered the analysis of each sample separately; 2) estimated ancestry and genetic background diversity from the genetic data and controlled for it in the association studies; and 3) looked for evidence of genetic background x SNP interactions. In order to qualify our results, we also compared them to previous GWA study results investigating BD, performed replication genotyping of our most strongly associated SNPs on an independent cohort, and conducted analysis of only the non-overlapping subjects in our study (with another study’s subjects) in order to tease out independent evidence for associations.
