Statistics
The distributions of continuous variables were tested for normality with the Kolmogorov-Smirnov test, and the difference between two groups was compared by student’s t-test or Mann-Whitney test wherever appropriate. Chi-squared test or Fisher exact test was used to compare the categorical variables. Moreover, Bonferroni adjustment was also applied in multiple comparisons. All analyses were 2-tailed, and P value < 0.05 was considered statistically significant. All the statistical data were analyzed using SPSS 20.0 (SPSS Inc., Chicago, IL, USA).