Clara cell protein in bronchoalveolar lavage fluid: a predictor of ventilator-associated pneumonia?

Introduction

Clara cell protein 10 (CC-10) is a low-molecular-weight protein secreted in large quantities by nonciliated Clara cells. Differences in CC-10 concentrations have been demonstrated in several inflammatory lung diseases (for example, bronchial asthma and chronic eosinophilic pneumonia). Moreover, there is evidence that in infectious pulmonary diseases the type of microorganism (for example, Pseudomonas aeruginosa) influences CC-10 activity. In this study we evaluated the presence of CC-10 in bronchoalveolar lavage (BAL) fluid as a potential marker for ventilator-associated pneumonia (VAP) in critically ill patients with a suspicion of VAP.

Methods

Between January 2003 and December 2007 all consecutive BAL fluid samples from critically ill patients in the ICU of the Maastricht University Medical Center clinically suspected of VAP were included. Patients were divided into two groups: microbiologically confirmed VAP (VAP group), and microbiologically not confirmed VAP (non-VAP group). VAP was microbiologically confirmed if BAL fluid cultures yielded ≥ 10⁴colony-forming units/ml and/or microscopic analysis revealed ≥ 2% intracellular organisms. The CC-10 concentration was measured with a commercially available ELISA, and retrospective analysis was performed. Areas under the curve of receiver operating characteristic curves were calculated for CC-10 concentrations.

Results

A total of 196 BAL fluid samples were included from 196 patients (123 men, 73 women). Seventy-nine out of 196 episodes of suspected VAP (40.3%) were microbiologically confirmed. The median CC-10 concentration in the VAP group was 3,019 ng/ml (range: 282 to 65,546) versus 2,504 ng/ml (range: 62 to 30,240) in the non-VAP group (P = 0.06), with an area under the curve of 0.586. In addition, CC-10 concentrations were not significantly different between the non-VAP group and the VAP group caused by a specific organism (for example, P. aeruginosa) (P = 0.386).

Conclusion

CC-10 concentration in BAL fluid is not a useful marker to differentiate between VAP and non-VAP.