Statistical analysis

Continuous data are shown as the group median (interquartile range), and categorical data are shown as the number (percentage) in the group. Fisher's exact test was used to compare categorical variables. The Mann–Whitney U‐test was used to compare continuous variables between two groups. A bivariate analysis of the categorical variables was carried out using a bivariate logistic regression analysis. The clinically important variables were included in this model regardless of their P‐values. A P‐value of <0.05 was considered to indicate statistical significance. All of the statistical analyses were undertaken using R (version 3.2.2; R Foundation for Statistical Computing, Vienna, Austria).