Soluble triggering receptor expressed on myeloid cells-1 in bronchoalveolar lavage is not predictive for ventilator-associated pneumonia

Introduction

The aim of the study was to evaluate the usefulness of soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) as a rapid diagnostic test for ventilator-associated pneumonia (VAP). To develop a rapid diagnostic test for the diagnosis of VAP, a common complication of mechanical ventilation [1], multiple biomarkers have been evaluated with variable results. sTREM-1 proved to be a good biomarker for sepsis [2]. For the diagnosis VAP, however, there have only been a few, relatively small, studies on the role of this receptor [3].

Methods

Retrospectively, 240 bronchoalveolar lavage fluid (BALF) samples, taken from patients in the ICU of a university hospital, were tested. sTREM-1 in BALF was measured using a quantitative sandwich enzyme immunoassay. Two researchers, unaware of the results of the assay, determined whether a VAP was present. Clinical suspicion of a VAP was confirmed by the presence of ≥ 2% cells containing intracellular organisms and/or a quantitative culture result of >10⁴ colony forming units/ml in BALF. The disease had to be acquired after at least 48 hours of mechanical ventilation.

Results

The mean concentration of sTREM-1 was significantly higher in BALF of patients with confirmed VAP compared with patients without VAP (P = 0.045). The area under the curve was 0.577 (95% CI = 0.503–0.651, P = 0.042). sTREM-1 levels in our hands proved not to be discriminative for VAP. Choosing a sensitivity of 95% resulted in a positive predictive value (PPV) of 41% and a negative predictive value (NPV) of 62% in our population. Taking a specificity of 95% led to a PPV of 67% and a NPV of 62%. sTREM-1 levels were not different in VAP cases caused by Gram-positive or Gram-negative bacteria. sTREM-1 levels were higher in nonsurvivors compared with survivors, regarding inhospital mortality.

Conclusion

The results imply that the sTREM-1 assay in BALF is not discriminative for VAP.