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1. Statistical Analysis
The statistical analysis of data was done by using excel (Microsoft Office 2013)
program and SPSS (statistical package for social science) program (SPSS, Inc,
Chicago, IL) version 20.
Kolmogorov-Smirnov test was done to test the normality of data distribution.
Significant data was considered to be nonparametric.
Qualitative data were presented as frequency and percentage. Chi square or Fisher
exact test were used to compare groups. Quantitative data were presented as mean
and standard deviation or median and range.
For comparisonbetween two groups; student t-test, and Mann-whitney test (for non
parametric data) were used. For comparison between more than two groups;
ANOVA and Kruskal wallis (for non parametric data) were used.
Kaplan–Meier test was used for survival analysis and the statistical significance of
differences among curves was determined by Log-Rank test.
Cox regression analysis of factors potentially related to survival was performed to
identify which independent factors might jointly have a significant influence on
survival.
Diagnostic performance was determined by constructing a ‘‘receiver-operating
characteristic’’ (ROC) curve and calculating the area under the ROC (AUROC)
curve. From these curves, the best cut-off values was established, which were the
values that maximized the sum of the sensitivity and specificity to identify patient
status.
N.B: p is significant if ≤0.05 at confidence interval 95%.