We used the results from a meta-analysis using only the three Finnish cohorts to predict the four TCI scales in the QIMR sample, using the ‘score' function in PLINK.34 We restricted this analysis to the same set of SNPs used in the full meta-analysis, and used only one individual per family. The ‘risk score' for individuals in the QIMR sample was constructed by multiplying the number of copies of the effect allele at each SNP by the Z-score from the Finnish-only meta-analysis of a given scale, and summing across SNPs. The observed TCI score in the QIMR sample was regressed on this risk score to assess the degree to which variability in the observed phenotype could be explained by variability in the risk score. The risk score was calculated using all SNPs, and also using the top 10, 20, 30, 40 and 50% of SNPs in the Finnish-only meta-analysis.
