ROC of sTREM-1, nTREM-1, m-TREM-1 and CRP to differentiate whether a chest X-ray infiltrate is due to CAP or to a non-infectious process is shown in Figure  2 . Area under curve (AUC) of sTREM-1 was 0.771 ± 0.068 (95%CI: 0.63 -0.9, p = 0.001). Sensitivity and specificity to diagnose between a pulmonary infiltrate of infectious origin and a pulmonary infiltrate of non-infectious origin were 82.6% and 63% respectively at concentrations above 19.53 pg/ml. AUC of nTREM-1 and mTREM-1 were 0.778 ± 0.063 (95%CI: 0.65 -0.9, p = 0.001) and 0.712 ± 0.07 (95%CI: 0.56 -0.86, p = 0.009) respectively. Sensitivity and specificity to diagnose between a pulmonary infiltrate of infectious origin and a pulmonary infiltrate of non-infectious origin were 78.3% and 58.6% for nTREM-1 above 2.55 MFI. Sensitivity and • Lung cancer (13) • Staphulococcus aureus (3) • Pulmonary embolism (6) • Haemophilus influenzae (2) • Congestive heart failure (5)