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Bronchoscopic BAL in the diagnosis of ventilator-associated pneumonia.

B ronchoscopic BAL has been used since 1988 in the diagnosis of ventilator-associated pneumonia (VAP). Quantitative cultures retrieved by protected and nonprotected bronchoscopic BAL have been reported to be accurate for the diagnosis of this frequent complication of mechanical ventilation. This section covers BAL methods that utilize fiberoptic bronchoscopy. We reviewed 23 studies evaluating the accuracy of BAL methods using fiberoptic bronchoscopy to diagnose VAP in a total of 957 patients. The number of reported VAP episodes was 431. Most reported studies are case series, although five immediate postmortem studies have been described since 1995. Patient enrollment was prospective, but consecutive enrollment was used in only four studies. The duration of mechanical ventilation is described in most studies as lasting from 1 to 90 days. In most cases, except in the postmortem studies, investigators assessing the test results and reference tests were aware of the patients’ clinical histories. The techniques and bacteriologic methods used are well described, but in some studies the microbiological or BAL methods are referenced to prior publications. BAL technique is not completely standardized. The amount of liquid instilled varies roughly from 130 to 150 mL. The first aliquot usually is discarded, and the rest are pooled for quantitative bacterial analysis. Serial dilutions and calibrated loop methods have been used for quantitative cultures. Four studies have used protected bronchoscopic methods with balloon occlusion, and one study employed the mini-BAL technique via fiberoptic bronchoscopy. Only two studies assessed the quality of BAL specimens, and they did so by the detection of squamous epithelial cells. No study assessed the presence of ciliated bronchial cells to indicate contamination by upper airway secretions. In most studies, BAL was compared with either bronchoscopic procedures (usually the protected-specimen brush [PSB] technique) or nonbronchoscopic methods (usually endotracheal aspiration and other blinded techniques). Most studies also used quantitative bacterial cultures to distinguish colonization from infection. For that purpose, the most frequent cutoff point was 10 cfu/mL. Information regarding prior antibiotic administration is lacking from some studies, but 457 patients are known to have received such treatment. The reference test “gold standard” is not standardized and varies among studies. Most studies combine clinical, microbiological, and histologic parameters. Immediate postmortem studies have used histology studies, lung cultures, or both. These studies are of particular value. The calculated sensitivity and specificity vary among studies, depending mainly on prior antibiotic treatment, type of study population, and the reference test employed. Some studies do not clearly state how sensitivity and specificity were calculated. Few studies reported receiver operating characteristic curves.