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.).