ROLE OF QUANTITATIVE CULTURES OF ENDOTRACHEAL ASPIRATES IN THE DIAGNOSIS OF NOSOCOMIAL PNEUMONIA

To assess the reliability of quantitative cultures of endotracheal asp irates (EA) to diagnose,ventilator-associated pneumonia, fiberoptic br onchoscopy was used to study 57 episodes of suspected lung infection i n 39 patients with no recent changes in antimicrobial chemotherapy. A total of 19 cases (33%) of pneumonia were diagnosed based on the follo wing criteria: protected specimen brush (PBS) sampling yielding greate r than or equal to 10(3) cfu/ml of at least one microorganism and/or g reater than or equal to 5% of cells containing intracellular bacteria on direct examination of bronchoalveolar lavage (BAL). The operating c haracteristics of EA cultures were calculated over a range of cutoff v alues (from 10(3) to 10(7) cfu/ml), and the threshold of 10(6) cfu/ml appeared to be the most accurate, with a sensitivity of 68% and a spec ificity of 84%. Microorganisms cultured from EA samples correlated wea kly with those obtained using PSB specimens (rho = 0.32), with only 49 microorganisms among 123 (40%) found in both samples. These latter re sults and the relatively low sensitivity of the technique indicate tha t EA quantitative cultures are of limited value for the diagnosis of p neumonia in ventilated patients when fiberoptic techniques are availab le.