Abstract
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.
Highlights
Differential diagnosis of patients with lung infiltrates remains a challenge
The results of the present study indicate that Triggering receptor expressed on myeloid cells (TREM)-1 can be used as marker of bacterial infection in patients with lung infiltrates. sTREM-1, nTREM-1, mTREM-1 and C-reactive protein (CRP) were comparable to their discriminating ability between a pulmonary infiltrate of infectious origin and a pulmonary infiltrate of non-infectious origin. sTREM-1 levels were decreased within the first 48 hours in patients with community acquired pneumonia (CAP) with favourable outcome probably after the initiation of appropriate therapy followed by improvement of clinical symptoms
Binding of its ligand is possibly linked to the activation of several transcription complexes that synergize with NF-B in order to elicit transcription of genes of pro-inflammatory cytokines [8]. sTREM-1 is the soluble counterpart of TREM-1 and it is probably shed in the systemic circulation from cell membranes of neutrophils and monocytes [7,33,34]
Summary
Differential 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. It is difficult to Triggering receptor expressed on myeloid cells (TREM)-1 is a recently described receptor on neutrophils and monocytes It behaves like a pattern recognition receptor (PRR) since its activation leads to the release of pro-inflammatory cytokines, namely of tumour necrosis factor-alpha (TNFa) and of interleukin (IL)-8. A soluble form of TREM-1, namely sTREM-1, is increased in the bronchoalveolar lavage (BAL) of patients with ventilator associated pneumonia (VAP) [5,6], and in the serum of patients with sepsis, with bacterial meningitis and with acute pancreatitis [7,8,9,10,11,12]. Increase of sTREM-1 seems particular prominent when the latter non-infectious states are complicated with systemic inflammatory response syndrome (SIRS) without infection [13,14,15,16,17,18,19]
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