Statistical Analysis
Quantitative data following a normal distribution are displayed as
mean±Standard deviation and compared using the Student t-test and the
ANOVA (Analysis of Variance) for two and three comparisons,
respectively. Quantitative data not following a normal distribution are
displayed as median (interquartile range) and compared using the
Mann-Witney and the Kruskal-Wallis tests for two and three comparisons,
respectively. Qualitative variables are displayed as percentages and
compared by χ2 or Fisher exact test when appropriate.
Univariate Cox regression analysis was used to study the predictive
power of the variables studied. Multivariate Cox regression analysis was
performed including all variables showing p<0.20 at univariate
analysis.
Analyses were performed with R v3.5.1 (R foundation for Statistical
Computing, Viena, Austria) and SPSS 19.0 (SPSS Inc., New York)..
Statistical significance was set at p<0.05 (two-tailed).