Statistical analysis
For the descriptive analysis, frequencies and percentages were used for
the qualitative variables, and mean and standard deviation (SD) or
median and interquartile range (IQR) for the quantitative variables.
Baseline characteristics of the intention to treat (ITT) population were
compared between the control group and the intervention group. In
addition, the main clinical outcomes up to one month follow-up in the
per protocol population (PP) were compared between the two groups. The
main results in follow-up up to one year were compared between the two
groups using both ITT and PP. The main events were also compared between
the different participating hospitals. To compare the qualitative
variables the Chi-square test or Fisher’s exact test were used, whereas
the t-test or Wilcoxon’s non-parametric test were used to compare the
quantitative variables. Finally, the main outcomes were compared between
the control group and the intervention group, adjusting for the Charlson
comorbidity index, using the logistic regression model. Kaplan-Meier
curves were drawn for one-year mortality in each group of patients and
these were compared using the log-rank test.
Biomarker levels were compared between the two groups of patients on
days 1, 5 and 30, as well as the difference from day 5 to day 30, using
the Wilcoxon non-parametric test. Biomarker differences from day 5 to
day 30 were also compared between the two groups of patients, adjusting
for biomarker levels on day 5, using the general linear model. On the
other hand, the effect of the difference in biomarkers from day 5 to day
30 on cardiovascular events at 1 year was analyzed, adjusting for
biomarker levels on day 5 and the Charlson index, using the logistic
regression model. Finally, we analyzed if this effect was different
depending on the group. For this analysis, the logistic regression model
was also used, considering the cardiovascular event as the dependent
variable, and as independent variables: the difference in biomarker from
day 5 to day 30, the group (intervention vs. control), the interaction
between the difference and the group, as well as the adjustment
variables for the Charlson index and the biomarker on day 5.
All results were considered statistically significant for p
<0.05. Analyses were performed using SAS for Windows, version
9.2 (SAS Institute, Cary, NC) and S-Plus 2000 (MathSoft Inc., Seattle,
WA, 1999).