Statistical analysis
Categorical variables are expressed as number of patients and
percentages and quantitative variables as median and interquartile range
[IQR]. The Kolmogorov–Smirnov test was used to determine whether
quantitative variables were normally distributed. The Chi-square test
(χ2) was used to compare qualitative variables (when the expected number
of cases in any of the cells was lower than 5, the Fisher exact test was
used) and the Student’s T test to compare normally distributed
quantitative variables (the Mann-Whitney U test for the non-normally
distributed ones). A logistic regression analysis was performed to
assess variables associated with the composite end-point of mortality or
ICU admission. This analysis was adjusted for variables that were
statistically significant (p<0.05) in the bivariate analysis
and those risk factors previously described in the literature (arterial
hypertension and obesity). A 2-sided α of less than 0.05 was considered
statistically significant. Analyses were performed with the software
Statistical Package for Social Sciences (SPSS) version 20.0 (SPSS, Inc.,
Chicago, Illinois, USA).