In all analyses, only autosomal biallelic SNPs with minor allele frequencies (MAF) of at least 1%, an info score above 0.8 and call rates above 98% were retained, which led to 5,508,534 SNPs. The present analysis includes only individuals with European ancestry, which was reported by patients, to minimize the risk of confounding due to ancestry differences(Price et al., 2006). A principal components analysis was applied in a linkage-disequilibrium-pruned set of genotyped SNPs to characterize population structure within samples of European ancestry.
