Statistical analysis
Measured values of the results were expressed as mean with standard deviation and median with interquartile range (IQR). Comparisons between means of continuous variables were determined using the Student t test, and Mann–Whitney U test as appropriate and between groups of dichotomous variables using the Chi-square test or Fisher's exact test. Paired-sample t tests and Wilcoxon signed-rank test were used for continuous variables and presented by the relative risk of 95% confidence intervals and median change with IQR. Statistical analyses were performed using SPSS Program for Windows, Version 15 (SPSS Inc, Chicago, IL, USA). A p < 0.05 was considered statistically significant.