Usefulness of microscopic examination of intracellular organisms in lavage fluid in ventilator-associated pneumonia.

Study Objective: To assess the usefulness of quantification of bronchoalveolar lavage (BAL) cells containing intracellular organisms (ICO) in the diagnosis of ventilator-associated pneumonia.

Design: The reliability of cytologic analysis in comparison with the protected specimen brush (PSB) and BAL quantitative cultures has been assessed in a prospective study.

Setting: An intensive care unit of a tertiary-referral teaching hospital.

Patients: A total of 33 ventilated patients with suspected pneumonia based on clinical grounds and radiographic findings.

Interventions: All patients underwent fiberoptic bronchoscopy within the first 24 h after clinical suspicion of pneumonia. Specimens were obtained by PSB and BAL and were processed for quantitative cultures using standard methods. Two 0.5-ml samples of resuspended original BAL fluid were centrifuged and stained with Gram and modified May-Grünwald-Giemsa for differential cell counts and percentage of cells with ICO.

Results: Pneumonia was the final diagnosis in 16 (49 percent) of the 33 patients. In 14 (42 percent) patients, pneumonia was excluded and in the remaining 3 the diagnosis was uncertain. Twelve of the 16 patients with pneumonia had their conditions diagnosed by PSB, 14 by BAL, and 10 by quantification of ICO. Only one patient's condition was diagnosed exclusively by cytologic examination. There were no false-positive results with any of the diagnostic techniques.

Conclusions: Microscopic identification of ICO in cells recovered by BAL allows early and accurate diagnosis of pneumonia in mechanically ventilated patients. However, the sensitivity of this technique is lower than with either PSB or BAL.