Possible replication of our association results was assessed using summary statistics for 1331 individuals of African-American ancestry and 1814 individuals of European-American ancestry, tested for genome-wide association with opioid dependence by Gelernter and colleagues [13]. The study samples had been ascertained at five different US sites and all subjects had satisfied the DSM-IV criteria of opioid dependence with the Semi-structured Assessment for Drug Dependence and Alcoholism [27] and provided written, informed consent as described in Gelernter et al [13]. GWAS had been performed on the Illumina HumanOmni1-Quad v1.0 chip. For our replication assessment, we prioritized the top 100 SNPs from our imputed association results and limited our replication to SNPs located within or close to the top genes, CCDC42 and BRSK2. Prior to the assessment, we checked for concordance of marker locations between the two datasets. A total of 49 SNPs were examined for replication, 24 markers in CCDC42 and 25 markers in BRSK2. In addition to the SNP-based replication, we were interested in assessing the association status in our data of candidate genes that had been previously tested in
