The SNP rs1803274 was selected because it is a common variant, known as the K variant, that leads to a functional decrease in BChE activity [24]. The other two SNPs were selected on the basis of the linkage disequilibrium (LD) structure of the gene, allele frequency, and available Haplotype Map data (http://hapmap.ncbi.nlm.nih.gov/index.html.en). Genotyping was conducted by Prevention Genetics (Marshfield, Wisconsin, USA; http://www.preventiongenetics.com/). For all genotypes, the Hardy-Weinberg equilibrium was assessed using the Haploview software, version 4.2 [27]. To estimate the statistical power of the sample, we used the QUANTO program, version 1.2, assuming an odds ratio (OR) of 1.5, a disease prevalence of 0.03, a calculated average minor allele frequency of 0.27, and a significance level of 0.05 [28].
