Statistical Analysis
Statistical analysis was performed with IBM SPSS 24.0 software.
Statistical results are presented as median (Q1-Q3) or mean ± standard
deviation. Baseline analysis among groups was performed with chi-square
tests or Fisher’s exact tests for categorical data and the 2-tailed t
test or the Mann–Whitney test for continuous data.
Multivariable
analysis was performed for variables that demonstrated statistical
significance in the univariable analysis. Logistics regression was used
for both univariate and multivariable analysis. Receiver operator
characteristic curves (ROC curves) were used for the determination of
the best cutoff point in predicting postoperative mortality. This cutoff
point was determined by maximizing the Youden index (=
sensitivity+specificity-1) of a ROC curve. Survival curves were plotted
using the Kaplan-Meier method, and statistical differences were compared
using a log-rank test. A P value less than 0.05 was considered
statistically significant.