Association analysis was performed using the pedigree disequilibrium test (PDT) (Martin et al. 2000, Martin, Bass & Kaplan 2001). This method provides valid and robust tests for allelic association across both trio and extended families. Only autosomal markers were tested for association. The estimation of odds ratios and 95% confidence interval calculations were performed using UNPHASED (Dudbridge et al. 2008). Power calculations for association analysis were performed using the Genetic Power Calculator (Purcell S, Cherny SS, Sham PC. 2008).
