Statistical analysis
The data are presented as median (interquartile range). Continuous variables were compared by Wilcoxon rank-sum test. Categorical variables were compared by an χ2 test or Fisher’s exact test. Significant differences were further evaluated by using Bonferroni’s method for pairwise multiple comparisons. A P-value < 0.05 was considered statistically significant. All statistical analyses were performed with R software (The R Foundation for Statistical Computing, Vienna, Austria).