SNP, the procedure weights the Z-score for each dataset by the case and control sample sizes and imputation r2 values (r2=1 for genotyped SNPs), while correcting for the shared controls between STAR*D and GenRED. Combined odds ratios were obtained with a similar procedure. This method takes into account the direction of association in the datasets (i.e., which allele is associated), assuming that the same allele should be associated in samples with closely-related ancestries. This increases power compared with the classical procedure which ignores direction. For the primary analysis, P < 5 × 10−8 was considered the 5% genome-wide significance threshold.38–40
