Statistical analysis
Allele and genotype frequencies of each SNP were calculated by direct counting. Genotype and allele frequencies between groups were compared using the χ2 test and Fisher’s exact test when appropriate. For allelic associations, p values with Yates correction and odds ratio (OR) with 95% confidence intervals (CI) were calculated using Statcalc program (Epiinfo version 6.0.4, CDC, Atlanta, GA). Pair-wise LD (D’, r2) was estimated by use of Haploview software version 4.2. For categorical data, chi-square tests were performed, while the student’s t -test (or Mann Whitney U test where appropriate) was performed to compare the continuous data. Differences in mean with a p value <0.05 were deemed significant. Standard errors of the means (and/or deviations) were also calculated