Genotypes were previously checked for quality by concordance between monozygotic twins and percent of genotypes successful for each individual and each SNP, tested for Hardy Weinberg equilibrium, and linkage disequilibrium between SNPs was estimated within ethnic groups using Haploview (Barrett et al., 2005), as previously described (Hoft et al., 2008).Two SNPs were rare, rs35389610 and rs4953 (minor allele frequencies = 0.006 and 0.04), and were removed from subsequent analyses. Phenotype descriptors and summary statistics were generated in SPSS version 16.0 and SAS version 9.1.
