Diagnosis of Gram negative, ventilator associated pneumonia by assaying endotoxin in bronchial lavage fluid

Abstract

Aim - To investigate the usefulness of assaying endotoxin in non-directed bronchial lavage fluid (NBL), bronchoscopic bronchoalveolar lavage fluid (BAL), and sera as a means of diagnosing Gram negative, ventilator associated pneumonia. Methods - Samples from 64 patients were investigated. Fifty nine BALs and 92 NBLs were assayed in total including specimens taken during 28 episodes of clinical ventilator associated pneumonia (VAP). Results - The concentration of endotoxin in BAL from patients with VAP developing within four days of commencing ventilation was significantly higher than in those without VAP (p = 0.015). There was no significant difference in endotoxin concentration in NBL or serum when comparing patients with and without VAP. A BAL endotoxin concentration of 6 EU/ml yielded the optimal operating characteristics (sensitivity, 81%; specificity, 87%; positive predictive value, 67%; negative predictive value, 95%). However, Gram stain of BAL provided the same information as quickly as the endotoxin assay and is considerably cheaper. Conclusions - Despite its accuracy and rapidity, the BAL endotoxin assay must be shown to alter clinical management and patient outcome to be cost effective.