Soluble triggering receptor expressed on myeloid cells (s-TREM-1) from endotracheal aspirates in critically ill patients: A potential marker of the dynamic inflammatory burden of the lower respiratory tract

Abstract

Objectives. The study was designed to evaluate the role of soluble triggering receptor expressed on myeloid cells (s-TREM-1) measured in samples of endotracheal aspirates from critically ill, intubated patients as a marker of inflammation or pneumonia. Methods. The Clinical Pulmonary Infection Score (CPIS), a commonly utilised clinical predictor of ventilatorassociated pneumonia (VAP), was calculated for each patient at the same time as endotracheal aspirates were obtained using sterile techniques, in order to correlate the CPIS with s-TREM-1 concentrations determined in the laboratory using a validated enzyme-linked immunosorbent assay (ELISA) procedure. Results. Thirty patients with intensive care unit stays ranging from 2 to 39 days were included in the study. s-TREM-1 was detectable in endotracheal aspirates from all patients, and a wide range of concentrations from 13 to >4 000 pg/ml was observed. The mean s-TREM-1 concentrations for patients with a CPIS <6 (N=15) and for those with a CPIS ≥6 were 592 (standard error of the mean (SEM) 288) and 382 (SEM 119) pg/ml, respectively (p>0.05). Conclusions. s-TREM-1 is readily detectable and quantifiable in endotracheal aspirates from critically ill patients, but does not correlate with the CPIS. The wide range of measured s-TREM-1 concentrations suggests that this pro-inflammatory marker may reflect a progressive increase in the dynamic inflammatory burden of the lower respiratory tract as colonisation by microbial pathogens leads to ventilator-associated tracheobronchitis (VAT) and ultimately VAP. Serial determinations of s-TREM-1 in this setting may therefore be of greater value than the CPIS in differentiating VAT from VAP and provide an alternative threshold for the initiation of empiric antimicrobial therapy.