The testing dataset was comprised of 288,978 UK Biobank Phase 2 participants distinct from those in the validation dataset described above. Individuals in the UK Biobank underwent genotyping with one of two closely related custom arrays (UK BiLEVE Axiom Array or UK Biobank Axiom Array) consisting of over 800,000 genetic markers scattered across the genome.15 Additional genotypes were imputed centrally using the Haplotype Reference Consortium resource, the UK10K panel, and the 1000 Genomes panel. In order to analyze individuals with a relatively homogenous ancestry and owing to small percentages of non-British individuals, the present analysis was restricted to the white British ancestry individuals. This subpopulation was constructed centrally using a combination of self-reported ancestry and genetically confirmed ancestry using principal components. Additional exclusion criteria included outliers for heterozygosity or genotype missing rates, discordant reported versus genotypic sex, putative sex chromosome aneuploidy, or withdrawal of informed consent, derived centrally as previously reported.15
