Statistical analyses were performed using SPSS for Windows (version 16.0; SPSS, Chicago, IL, United States). Means and standard deviations were calculated for continuous variables. Dosages of LTG intake were described as median and interquartile range (IQR). To detect differences in the clinical characteristics between the case and control groups, an independent t-test was used for continuous variables. Chi-square test and Fisher’s exact test were used to describe the differences in frequencies of the HLA-A, B alleles between the groups. Haplotype association analysis was carried out using the “haplo.stats” package. The level of statistical significance was set at p < 0.05 (two-sided).