Objective: To validate sampling techniques (tracheobronchial aspirates, protected specimen brush, and bronchoalveolar lavage, both conventional and protected) for the detection of ventilator-associated pneumonia (VAP) and causative microorganisms according to different histologic and microbiological references.
Design: Immediate, multiple bilateral lung biopsy, postmortem study.
Setting: Respiratory intensive care unit of a 1,000-bed teaching hospital.
Patients: Twenty-five mechanically ventilated patients (>72 hrs) who died in our intensive care unit.
Measurements: Lung tissue histologic examination and quantitative cultures (16 specimens/patient). The following four references for the diagnostic techniques were used: histology of guided lung biopsy, histology of blind lung biopsy, combined guided and blind lung biopsy histology and microbiology of lung tissue, and microbiology of lung tissue.
Results: Sensitivities when histologic reference tests were used ranged from 16% to almost 40%, whereas specificity rates were always <80%. When we combined both lung histology of guided or blind specimens and microbiology of lung tissue, all diagnostic techniques achieved considerably higher but still limited diagnostic yields (sensitivity range 43% to 83%; specificity range 67% to 91%). Causative organisms were missed in a significant number of cases by all techniques (17% to 83%).
Conclusions: The diagnostic performances of different diagnostic techniques strongly depend on the reference used. All techniques for detecting VAP are of limited value. Finding a balance between clinical judgment and microbiological results is crucial to appropriately manage patients with VAP.