Statistical Analysis
Statistical analyses were performed using SPSS (version 19.0 program for Windows; SPSS Inc., Chicago, IL, USA). Categorical datas were presented as numbers (percentage) and tested using the Chi-square test or Fisher’s exact test. Continuous variables with normal distribution were presented as mean ± SD (standard deviation) and tested with a paired t-test. The chi-square test was used to compare categorical variables between the groups. Correlations between numerical variables were evaluated using Pearson’s or Spearman’s correlation analysis. We selected correlation strength by an absolute correlation |r|>0.2. P-values based on two-sided tests were considered as statistically significant at less than 0.05.