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 comparison between 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%.