BAL is a powerful diagnostic tool if its triad are fulfilled: adequate specimen, prompt processing and a patholgist knowing what he is looking for. In normal BAL, fluid recovery of about 60% with total cell count 175+/-30/mm3 is usually obtained. This count is increased in alveolitis (832+/-221/mm3). While it is markedly reduced in bone marrow transplant, immunocompromised patients and in patient with diffuse alveolar damage (DAD). The normal differential for BAL is Free Alveolar Macrophages (FAM�s) 87%; neutrophils (PMN) 3% Lymphocytes 10% (reduced in smokers to less than 7%). Esoinophils are less than 0.5%. Lymphocytic alveolitis in BAL is seen in hypersensitivity pneumonitis, sarcoidosis, tuberculosis, carcinomatosis (in 45% of malignant cases), drug induced lung disease, collagen vascular disease and less commonly in asbestosis, AIDS, alveolar proteinosis and in inorganic dust exposure. Neutrophilic alveolitis is seen in active T.B, idiopathic pulmonary fibrosis, ARDS, collagen vascular disorders, diffuse pan bronchiolitis, pneumoconiosis and smokers. Esinophilic alveolitis with marked increase in eosinophils is seen in eosinophilic pneumonia, allergic bronchopulomnary aspergillosis, asthma bronchiale, Churg- Strauss syndrome, but it can be seen coupled with neutrophils in cryptogenic and secondary fibrosis and in idiopathic pulmonary fibrosis, scleroderma, and Wegner�s granuloma. Multinucleate giant cells can be seen in normal BAL and do not indicate a specific disease entity. Hemosiderosis, on the other hand, can be of important diagnostic pattern. It is increased in smokers, heart failure and more abundant in alveolar hemorrhage, and vasculitis of different patterns. CD4/CD8 ratio is of great diagnostic value in BAL. It is increased in sarcoidosis, asbestosis, and berylliosis. Decreased in hypersensitivity pneumonitis, silicosis, drug induced lung disease and in AIDS. It is normal in T.B and in carcinomatosis. In idiopathyic pulomary fibrosis or fibrosing alveolitis: increased eosinophils and neutrophils is seen in progressive cases. PMN of <6% indicate a remission. If >10% of PMN present, clinical deterioration seen in 50% of patients; stable disease in 37.5% , and improvement in 12.5%. Lymphocytosis indicates better response to therapy with clinical improvement seen in 40% of the cases, stable disease in 30% and deterioration in 30%. Treatment of conditions with PMN�s or eosinophils: may require cyclophosphomide in addition to steroids therapy. In bone marrow transplant with pulmonary symptoms, the presence of lymphocytosis in BAL indicates better outcome, especially if combined with free alveolar macrophages that are negative for hemosiderin deposition. Different diseases may have different BAL patterns. In sarcoidosis: lymphocytosis is seen in over 75% of cases with average percentage of lymphocytes 27%. CD4/CD8 ratio of 4 or above is almost diagnostic of sarcoidosis. In Rheumatoid lung diseaes: FAM�s are decreased to around 45%+/-5%. In extrinsic allergic alveolitis: the pattern depends on time of BAL in relation to exposure: with tendency to have more lymphocytes and less PMN as exposure becomes older, accompanied by increase in immunoglobulin. In scleroderma: 58% of the cases show increased PMNs +/-esinophils. In pulmonary embolism: there is increase in total protein, albumin, decrease in FAM�s and increase in PMN
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.Hussam Abu-Farsakh, M.D
American Board of Pathology and Cytopathology