Statistical analysis

Normal distributed data were expressed as the mean ± SD. Skewed data were presented as medians with interquartile ranges. Comparisons among groups were performed by one-way analysis of variance and Mann–Whitney U-test according to the distribution of data. Dunn’s multiple comparison test was used to analyze differences when equal variances not assumed. The independent Student’s T-test and Mann–Whitney U-test were used for comparisons of two groups according to the distribution of data. The best TNAP cutoff was that of the highest product of sensitivity and specificity for in-hospital mortality prediction. Cumulative incidence curves of in-hospital mortality were estimated using the Kaplan–Meier product–limit estimation method with the log-rank test. Cox proportional hazards model was used to analyze the independent effect of TNAP on in-hospital and follow-up mortality. All data analyses were performed by SPSS 22.0 statistical software. Statistical significance was defined as P < 0.05.