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).