What tests can be performed on Bronchoalveolar Lavage (BAL) fluid?

From the Guidelines

Bronchoalveolar lavage (BAL) fluid should undergo differential cell count, including macrophage, lymphocyte, neutrophil, and eosinophil cell counts, as well as microbiology, virology, and/or malignant cell cytology laboratory testing if clinically indicated. This is based on the recommendation from the American Thoracic Society clinical practice guideline 1. The tests that can be performed on BAL fluid include:

• Differential cell count to identify inflammatory patterns
• Microbiological testing, such as cultures for bacteria, fungi, and mycobacteria, as well as PCR for viruses and atypical pathogens
• Cytology examinations to detect malignant cells
• Immunological tests, such as CD4/CD8 ratios, to help diagnose conditions like sarcoidosis
• Additional specialized tests, including biomarker analysis, genetic testing, and evaluation of inflammatory mediators, may be useful in certain clinical scenarios. However, according to the most recent guideline from the European Respiratory Society 1, BAL should include differential cell count, periodic-acid-Schiff (PAS)-staining, and microbiology. This suggests that the selection of specific tests depends on the clinical suspicion, and the results are typically available within 24-72 hours for most routine tests.

From the Research

Tests Performed on Bronchoalveolar Lavage (BAL) Fluid

The following tests can be performed on BAL fluid:

• Cytologic examination to diagnose primary and metastatic lung cancer 2
• White blood cell (WBC) profiles to determine the presence of respiratory pathogens and diagnose diffuse lung diseases 3
• Molecular assays such as polymerase chain reaction (PCR) or enzyme-linked immunosorbent assay to diagnose specific lung disorders 4
• Special cytopathologic stains to identify specific cell types and diagnose lung diseases 4
• Differential cell counts to enumerate cell types, including polymorphonuclear neutrophils, alveolar macrophages, lymphocytes, and eosinophils 5
• Culture to diagnose fungal infections 6
• Cytologic and morphologic analysis to diagnose fungal infections 6

Diagnostic Applications of BAL Fluid Analysis

BAL fluid analysis can be used to:

• Diagnose primary and metastatic lung cancer 2
• Diagnose diffuse lung diseases, such as interstitial lung disease (ILD) 3
• Monitor lung allografts 3
• Evaluate pediatric lung disease 3
• Diagnose respiratory infections, including fungal infections 3, 6

Technical Considerations for BAL Fluid Analysis

Technical considerations for the performance of BAL for diagnostic purposes include:

• Methods to assure lavage of the appropriate segment 2
• The type of cytologic preparation and stain used 2
• Conditions such as viral infections and anti-neoplastic chemotherapy, which can induce changes in airway epithelial cells 2
• The optimum technique for the performance of lavage 2