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.