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.