• Ilias Porfyridis, Diamantis Plachouras, Vasiliki Karagianni, Anastasia Kotanidou, Spyridon A Papiris, Helen Giamarellou, and Evangelos J Giamarellos-Bourboulis.
• Department of Critical Care and Pulmonary Services, National and Kapodistrian University of Athens, Evangelismos Hospital, Athens, Greece. ilias_porfi@yahoo.gr
• Bmc Infect Dis. 2010 Jan 1;10:286.

BackgroundDifferential diagnosis of patients with lung infiltrates remains a challenge. Triggering receptor expressed on myeloid cells (TREM)-1 is a neutrophil and monocyte receptor up-regulated during infection. The aim of this study was to evaluate the diagnostic accuracy of TREM-1 and of C-reactive protein (CRP) from patients with lung infiltrates to discern community acquired lung infections.Methods68 patients admitted to a medical ward with acute respiratory illness were enrolled in the study. Neutrophil and monocyte TREM-1 expression were measured by flow cytometry, sTREM-1 by an enzyme immunoassay and C-reactive protein by nephelometry. Clinical pulmonary infection score was recorded.Results34 patients were diagnosed with bacterial community acquired pneumonia (group A) and 34 with non-bacterial pulmonary disease (group B). Median serum TREM-1 concentration was 102.09 pg/ml in group A and lower than 15.10 pg/ml (p < 0.0001) in group B. Mean±SE neutrophil TREM-1 expression was 4.67 ± 0.53 MFI in group A and 2.64 ± 0.25 MFI (p = 0.001) in group B. Monocyte TREM-1 expression was 4.2 ± 0.42 MFI in group A and 2.64 ± 0.35 MFI (p = 0.007) in group B and mean±SE CRP was 18.03 ± 2 mg/ml in group A and 7.1 ± 1.54 mg/ml (p < 0.001) in group B. A cut-off of 19.53 pg/ml of sTREM-1 with sensitivity 82.6% and specificity 63% to discriminate between infectious and non-infectious pulmonary infiltrates was found. sTREM-1 at admission greater than 180 pg/ml was accompanied with unfavourable outcome.ConclusionTREM-1 myeloid expression and sTREM-1 are reliable markers of bacterial infection among patients with pulmonary infiltrates; sTREM-1 is a predictor of final outcome.

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