From the Guidelines
Bronchoalveolar lavage (BAL) fluid can be analyzed with multiple laboratory tests, including cell count and differential, microbiological studies, cytology, flow cytometry, and measurement of inflammatory markers, to diagnose various pulmonary conditions, as recommended by recent guidelines 1. The choice of specific tests depends on the clinical suspicion, with results interpreted in the context of the patient's clinical presentation and other diagnostic findings. Some of the key tests that can be run on BAL fluid include:
- Cell count and differential to identify inflammatory patterns, with neutrophil predominance suggesting infection and eosinophil elevation indicating allergic processes
- Microbiological studies such as Gram stain, cultures (bacterial, fungal, mycobacterial), and PCR testing to identify infectious pathogens
- Cytology and flow cytometry to detect malignant cells and characterize lymphocyte populations
- Measurement of inflammatory markers like IL-8 and TNF-alpha, evaluation of protein content and albumin levels to assess alveolar-capillary permeability
- Specialized tests like PCP staining for Pneumocystis pneumonia or galactomannan for invasive aspergillosis
- In suspected interstitial lung diseases, CD4/CD8 ratios can be helpful, with elevated ratios suggesting sarcoidosis, as noted in earlier guidelines 1. Recent guidelines also recommend the use of BAL for the diagnosis and management of pulmonary alveolar proteinosis, including the use of periodic-acid-Schiff (PAS)-staining and microbiology 1. The most recent and highest quality study recommends that BAL be performed as part of the diagnostic work up of patients with suspected PAP, including differential cell count, PAS-staining, and microbiology 1.
From the Research
Labs that can be run on Bronchoalveolar Lavage (BAL) Fluid
The following labs can be run on BAL fluid:
- Quantitative bacterial cultures to identify aerobic and anaerobic organisms 2
- Semiquantitative culture to identify the causative agent in acute bacterial pneumonia 3
- Gram stain to predict culture results and identify bacterial isolates 4
- Microbiological sampling to obtain samples from the lower respiratory tract and guide targeted antibiotic therapy 5
Types of Tests
Some of the specific tests that can be performed on BAL fluid include:
- Bacterial cultures to identify relevant bacteria 2, 3, 5
- Gram stains to identify Gram-positive and Gram-negative isolates 4
- Measurement of lidocaine concentrations to assess contamination 2
- Procalcitonin (PCT), C-reactive protein (CRP), and white blood cell (WBC) counts to evaluate infection 5
Clinical Applications
BAL fluid analysis can be used in various clinical settings, including: