Diagnostic investigation of ventilator-associated pneumonia using bronchoalveolar lavage: comparative study with a postmortem lung biopsy

The purpose of the present study was to validate the quantitative culture a nd cellularity of bronchoalveolar lavage (BAL) for the diagnosis of ventila tor-associated pneumonia (VAP). A prospective validation test trial was car ried out between 1992 and 1997 in a general adult intensive care unit of a teaching hospital. Thirty-seven patients on mechanical ventilation with sus pected VAP who died at most three days after a BAL diagnostic procedure wer e submitted to a postmortem lung biopsy. BAL effluent was submitted to Gram staining, quantitative culture and cellularity count. Postmortem lung tiss ue quantitative culture and histopathological findings were considered to b e the gold standard exams for VAP diagnosis. According to these criteria, 2 0 patients (54%) were diagnosed as having VAP and 17 (46%) as not having th e condition. Quantitative culture of BAL effluent showed 90% sensitivity (1 8/20), 94.1% specificity (16/17), 94.7% positive predictive value and 88.8% negative predictive value. Fever and leukocytosis were useless for VAP dia gnosis. Gram staining of BAL effluent was negative in 94.1% of the patients without VAP(16/17). Regarding the total cellularity of BAL, a cut-off poin t of 400,000 cells/ml showed a specificity of 94.1% (16/17). and a cut-off point of 50% of BAL neutrophils showed a sensitivity of 90% (19/20). In con clusion, BAL quantitative culture, Gram staining and cellularity might be u seful in the diagnostic investigation of VAP.