Statistical analysis
Statistical analysis was performed using IBM SPSS Statistics for Windows v.23® (IBM Corp., Armonk, N.Y., USA). Continuous variables are shown as mean ± SD and median(range). One-way ANOVA was used to analyze parametric variables, versus the Kruskal-Wallis test for non-parametric quantitative variables. Comparison of categorical variables was performed using the Chi-square test. Correlation between non-parametric data was analyzed by Spearman’ correlation analysis. The level of statistical significance was set at p<0.05.