2.4 Statistical analysis
The Chi-square test or Fisher’s exact test was used to analyze
categorical variables, and t-test was used to analyze continuous
variables. All statistical tests were two-sided, and a p value of less
than 0.05 indicated statistical significance. The odds ratio (OR) and
95% confidence interval (CI) were also calculated. Statistical analyses
were performed with SPSS 20.0 software (SPSS, Chicago, IL, http:// www.
spss.com).