2.4. Statistical analysis
Data were analyzed using SPSS v. 25.0 (IBM, Armonk, NY). Continuous variables were expressed as the mean ± standard deviation and categorical variables were expressed as number of cases. After determining whether the data conformed to a normal distribution, normally distributed continuous variables were analyzed by one-way analysis of variance with post hoc tests. The Kruskal–Wallis test was performed for multiple sets of continuous variables not conforming to normal distribution. Categorical variables were compared using the chi-square test or Fisher’s exact test. 