*2.4. Statistical Analysis*

Data are shown as mean ± SD. For normally distributed parametric variables, comparison between two independent groups was performed using Student's *t* test, whereas *t*-test for related measurements was used for comparing patient features between different timepoints. For those parametric variables with non-normal distributions, the Mann–Whitney U test and the Wilcoxon test were used. To compare non-parametric variables, Chi square tests (independent groups) and McNemar tests (paired samples) were used. The relationships between quantitative normal variables were studied by linear correlation analysis (Pearson's r), whereas Spearman's rho was used for non-normally distributed variables. A value of *p* < 0.05 was chosen as the level of significance. The software used was Statistical Package for Social Sciences (SPSS v. 15.0. MapInfo Corporation, Troy, NY, USA).
