Statistical analysis
Data analysis was conducted using the SPSS software version 22. Quantitative variables were reported as mean, median, standard deviation, minimum and maximum, and qualitative variables were reported as frequency and percent. The normality of quantitative variables was assessed using the Shapiro-Wilk test. The chi-square or Fisher’s exact tests were used to compare the categorical and nominal variables between the two groups. The Mann-Whitney U test or t-test was also used for between-group comparisons of the quantitative variables according to the results of the normality test. The level of significance was set as < 0.05 in all tests.