In order to increase genomic coverage and allow the evaluation of the same SNPs across as many study populations as possible, each study imputed genotype data based on the HapMap CEU Build 35 or 36. Algorithms were used to infer unobserved genotypes in a probabilistic manner in either MACH, IMPUTE43, or software that was developed by the researchers. As a quality control measure, we excluded non-genotyped SNPs with an imputation quality less than 0.3 (for observed versus expected variance in MACH) or 0.4 (for IMPUTE’s proper info statistic) from the meta-analysis.
