COGA GWAS EA sample independent of the COGA family-based association sample were used to assess predictive accuracy of candidate gene sum scores. The FSCD and COGEND portions of the SAGE GWAS EA sample were extracted for use as a sample independent of COGA. Table 2 summarizes characteristics of the samples used in both study parts. Discriminatory accuracy of genetic sum scores and family history was measured using ROC curve analysis in SPSS/PASW v17.0 (SPSS Inc., Chicago IL) and the caTools package (Tuszynski, 2011) in R v2.12.2 (R Foundation, Vienna, Austria).
