Results are expressed as the mean ±SD. Comparisons of discrete variables were made using the chi-square test or Fisher's Exact Test. Student t-tests were used for continuous variables. Because the distribution was skewed due to a small study sample, non-parametric tests (Mann-Whitney test for unpaired variables and Wilcoxon-signed rank test for paired variables) were used. All statistical analysis was performed with SPSS 13.0. (SPSS Inc., Chicago, IL, USA). A value of p<0.05 was considered statistically significant.