Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1330 page)

   Quantitative bacterial cultures of specimens collected bronchoscopically (BAL or protected brush) are usually submitted for the evaluation for ventilator-associated pneumonia (VAP). The diagnosis of VAP is challenging, requiring a combination of clinical, imaging, and laboratory studies. Cultures are assessed in comparison to thresholds established by the laboratory in collaboration with clinicians.

   Special Collection and Transport Instructions

   Protected brush and BAL specimens are collected by a trained physician using standard procedures.

   Brush:

   The brush is inserted through a plugged catheter via the biopsy channel of the bronchoscope. After expulsion of the plug, the brush is used to collect cells and secretions from the distal airways.

   The brush end should be removed, using sterile technique, and placed in a small volume (1 mL) of nonbacteriostatic saline for transport.

   BAL:

   BAL specimens are collected by a trained physician using standard procedures. The procedure and placement of the tip may be done under direct visualization or “blindly” through an endotracheal tube (mini-BAL).

   The bronchoscope should be wedged in the terminal airways to ensure sampling of alveolar contents; return from the procedure should be 10–100 mL, sampling approximately 1 mL of alveolar secretions.

   Samples should be transported to the laboratory as quickly as possible, using standard protocols for bacterial cultures.

   Use

   Method:

   Known volumes of the specimen (or specimen dilutions) are inoculated onto solid agar media, including SBA, chocolate, and MacConkey agar (and other media as required for uncommon pathogens, such as
Legionella
); quantitative results are reported on the basis of the number of colonies isolated.