Values for nTREM-1, mTREM-1 and CRP are presented as mean ±SE; those of sTREM-1 are presented as medians and 95% confidence intervals (CI) or interquartile range (IQR). Comparisons between groups for nTREM-1, mTREM-1 expression and for CRP were done by ANOVA, followed by the Tukey's test for multiple comparisons. Comparisons of sTREM-1 between groups were done by Mann-Whitney U test after Bonferroni corrections for multiple comparisons. Comparisons of sTREM-1 between consecutive days within one group were done by Wilcoxon's signed rank test. Receiver Operator Curves (ROC) were designed to asses sensitivity, specificity, positive and negative predictive values for the estimated parameters to disclose infectious from non-infectious infiltrates. Patients were divided into two categories according to serum levels of sTREM-1 upon admission: those with sTREM-1 below or equal to 180 pg/ml; and those with serum sTREM-1 greater than 180 pg/ml. This concentration has been proposed as a threshold defining final prognosis in septic populations [22, 29] . Since CAP is a common cause of sepsis, this threshold was considered of merit. Survival was assessed by Kaplan-Meier and comparisons were done by log-rank test. Correlations between severity scores and measured parameters were done according to Spearman. Probability values less than 0.05 were considered statistically significant. All statistics and graphs were done using the Statistical Package for the Social Sciences software version 17.0.0 (SPSS Inc, Chicago, IL).