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-TERM-1) measured in samples of endotracheal aspirates from critically ill, intubated patients as a marker of inflammation of pneumonia. METHODS: The Clinical Pulmonary Infection Score (CPIS), a commonly utilised clinical predictor of ventilator-associated pneumonia (VAP), was calclated for each patient at the same time as endotracheal aspirates were obtained using sterile techniques, in order to correlate the CPIS with s-TERM-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-TERM-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-TERM-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-TERM-1 is readily detectable and quantifiable in endotracheal aspirates form critically ill patients, but does not correlate with the CIPS. The wide range of measured s-TERM-1 concentrations suggests that this pro-inflammatory maker 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-TERM-1 in this setting may therefore be of greater value than the CIPS in differentiating VAT from VAP and provide an alternative threshold for the initiation of empiric antimicrobial therapy.