1. Descriptive analysis Data are expressed as mean (SD), or median and 1st , 3rd quartiles, as appropriate for quantitative variables. Qualitative variables are expressed as total numbers and percentages Comparison of characteristics in each group was performed using χ2 test or Fisher exact test for qualitative variables. For quantitative variables, comparison involved the t.test or wilcoxon test. P<0.05 was considered statistically significant