Statistical analysis
The results are expressed as mean ± standard deviation or percentage, as appropriate. Student t-test or Mann-Whitney U test (used when data does not conform to a normal distribution) were used for independent samples, paired t-test or the Wilcoxon signed-rank test (used when data does not conform to a normal distribution) for paired data, and Mann-Whitney U test were used to compare continuous variables. Furthermore, χ2 or Fisher’s exact tests were used to compare nominal variables, as appropriate; Fisher’s exact test is used if one of the expected frequencies is less than 5, and the χ2 test is used if each frequency is greater than 5. Differences among the different groups were compared using one-way analysis of variance (differences between groups of 3 or more were examined). The Kaplan–Meier method was used to calculate survival free from the endpoint events. A log-rank test was used to compare survival curves among the different patient groups. Univariable and multivariable Cox regression analyses were used to assess the association of individual variables with combined endpoints. Age, sex, and variables with p <0.1 on univariate analysis were incorporated into a multivariate analysis. All the reported probability values were two-tailed, and a p-value <0.05 was considered statistically significant. SPSS version 24.0 Statistical software (IBM) and GraphPad Prism 7.0 (GraphPad Software Inc., La Jolla, CA, USA) were used for calculations and illustrations, respectively.