Fluid Analysis -Bronchoalveolar

What is a BAL cell count?

Main constituents of BAL are secretions from lung air spaces called as alveoli. Usual cell count is approximately 100cells/µL with majority being macrophages (>80%), followed by lymphocytes (<15%) and only small percentage is neutrophils (<3%) and eosinophils (<1-2%).

What does BAL test for?

BAL or bronchoalveolar washing is done to collect sample from lungs. This testing helps us to know the status of smaller bronchi and lung alveoli. It is done to see for pathological nature of the lung disease when patient is having symptoms like persistent cough, fever, breathing difficulty or hemoptysis (blood in coughing) and having any immune system disorder like HIV-AIDS or diabetes. BAL test helps in diagnosing different lung diseases like lung infections, TB, interstitial lung diseases, connective tissue diseases, fat embolism, lipoid pneumonia, occupational lung disease, pulmonary alveolar proteinosis, sarcoidosis and cancers (bronchus, lung or metastasis). BAL helps us to study cellular as wells as non-cellular constituents of lower respiratory tract and lung alveoli. It acts as window to evaluate lung parenchyma and any alteration in BAL fluid reflects pathological changes in lungs.

What are BAL cells?

Microscopic examination is done to study the cells in BAL fluid. Total and differential WBC count is given. Cell count is used for diagnosing infections. Increased neutrophils suggest active infection within the alveoli. However neutrophilia may also be seen in ARDS, connective tissue disorder, Wegener’s granulomatosis, pneumoconiosis or pulmonary fibrosis. Eosinophils may be higher in infections (parasites, fungal), bronchial asthma, interstitial pneumonias, and idiopathic hyper-eosinophilic syndrome. Lymphocytic predominance points towards TB, HIV infection, malignancy, hypersensitive pneumonitis, occupational disease and sarcoidosis. High levels of eosinophils and lymphocytes can be drug induced or in connective tissue disorders. Presence or absence of RBCs is reported. In case of alveolar hemorrhage, each subsequent BAL wash will continue to have RBCs. High RBC counts is seen in recent hemorrhage. Alveolar hemorrhage beyond 48 hours shows hemosiderin laden macrophages. Other cellular components like mesothelial cells, macrophages, atypical and malignant cells, if present, are mentioned. Amorphous looking material on slide microscopy with acellular debris favors diagnosis of pulmonary alveolar proteinosis. Reduced number of alveolar macrophages is seen in sarcoidosis.

What is the predominant cell type found in BAL?

Under normal circumstances, predominant cell type seen in BAL is alveolar macrophages.

What are the indications of doing BAL?

• Indications for BAL are: Long standing, non-resolving pneumonia
• Diffuse lung infiltrates in the lung alveoli or surrounding interstitium/lung parenchyma
• Any suspicion of alveolar hemorrhage
• In ventilator associated pneumonia for doing culture examination
• Any lung infiltrates in immunocompromised / weak immune system patients
• At times, for research purposes.