Statistical analysis
Categorical variables were presented as numbers and percentages and were analyzed by Pearson’s χ2 or Fisher’s exact test. Continuous variables were expressed as mean±standard deviation (SD) or median with interquartile range. Normality of the data was assessed using Shapiro-Wilk test. Differences between groups were compared using the Student’s test for normally distributed continuous variables and for non-normally distributed continuous variables the Mann-Whitney U test was used. Analysis of variance (ANOVA) was used to compare continuous variables across >2 groups. Associations between nonparametric and parametric variables were assessed by Spearman’s and Pearson’s tests, respectively. P-values of <0.05 were considered statistically significant. All statistical analyses were performed using JMP® Version 13.1.0 and SAS 9.4 (SAS Institute Inc.).