Primarily two methods exist for constructing genetic scores: count and weighted methods. The count method is the sum of the number of risk alleles, whereas the weighted method incorporates the sum of the number of risk alleles each weighted by its odds-ratio or effect size. In this study, the weighted scores were constructed from regression coefficients reported by Speliotes et al.[9]. Count and weighted scores using the proxy method were calculated using the profile option in PLINK [42]. If SNP information was missing in an individual then the scoring routine imputed expected values based on sample allele frequency. Count and weighted scores using imputed genotypes were constructed using R version 2.13.1(script available upon request to R.E.P.) [43]. Furthermore, to extend existing GRSS methodology [44], count and weighted scores were constructed using probabilities of imputed risk alleles (p) by the equation below (Equation 1). Count scores were calculated with β = 1 and weighted scores with β = effect size of each risk allele (A) reported by Speliotes et al.[9] summed over the number of risk alleles in the score (n).
