2.1 | Statistical analysis
Statistical analysis was conducted with SPSS 20 (SPSS, Chicago, IL). Kolmogorov-Smirnov test was used to determine the normality of distribution. Continuous variables were expressed as mean ± SD or median (25-75 IQR) and compared with Student t test or Mann-Whitney U test according to the distribution. Categorical variables were expressed as number and percentages and compared with chi-square or Fisher’s exact chi-square test. Multivariate logistic regression analysis with backward elimination was used to determine the independent predictors of mortality. Receiver operating characteristics (ROC) curve was performed to determine the area under curve (AUC) of variables for predicting mortality. The comparison of the AUCs were performed with Delong test. Ap value of less than 0.05 was considered as statistically significant.