Purpose: A prospective study to determine the usefulness of quantitative bacterial cultures of fluid obtained via fiberoptic bronchoscopy and bronchoalveolar lavage as an aid in the diagnosis of bacterial pneumonia.
Patients and methods: All patients undergoing fiberoptic bronchoscopy with bronchoalveolar lavage during a 6 1/2-month period. Presence of pneumonia was determined using clinical, radiographic, laboratory, and histologic data. Quantitative bacterial cultures of bronchoalveolar lavage fluid were determined using a 1-microL culture loop.
Results: Quantitative bacterial cultures of bronchoalveolar lavage (BAL) fluid were sensitive and specific predictors of bacterial pneumonia. Using 10(3) colony-forming units (cfu)/mL as the threshold value for a positive culture, we determined the sensitivity and specificity to be 90% and 97%, respectively. The data were also analyzed for the subgroups of patients who were intubated or were receiving antibiotics. The sensitivity and specificity were 78% and 96% for the group of patients receiving antibiotics and 100% and 82% for the group of patients intubated for more than 24 hours at the time of BAL. Values for the area under the receiver operating characteristic curve for the 3 groups were 0.94, 0.88, and 0.96, respectively.
Conclusions: Quantitative bacterial cultures of BAL fluid are sensitive and specific in the diagnosis of bacterial pneumonia. The use of antibiotics at the time of BAL reduces the sensitivity of the test, and prolonged intubation reduces the specificity of the test.