[Value of bronchoalvoeolar lavage in the diagnosis of lung disease].

Bronchoalveolar lavage (BAL) is an important tool for evaluating interstitial lung diseases. It provides information on inflammatory cells which play an important role in the pathogenesis of such diseases and complements the information of the lung biopsy. The method is based on the observation, that the cells recovered by BAL reflect the population of cells in pulmonary parenchyma. In healthy subjects the main cells in the lavage fluid are macrophages (> or = 80%), lymphocytes (10-20%), some few neutrophils (< or = 4%), eosinophils (< or = 3%) and single mast cells. There are significant differences in the distribution of cell types in never-smokers, exsmokers and current smokers. Generally the increase in the number of lymphocytes is a hallmark of granulomatous and allergic lung diseases. Evaluation of the lymphocyte surface antigen phenotypos allows the recognition of sarcoidosis (increased proportion of T-helper lymphozytes) and extrinsic allergic alveolitis (increased proportion of T-suppressor lymphocytes). High neutrophil counts are characteristic of fibrosing processes or of occupational diseases caused by inhalation of inorganic dust. The evaluation of the diagnostic accuracy of the BAL is difficult because the final diagnosis of many symptomatically cured patients is not clear. Nevertheless, the evaluation of our cases showed a surprisingly high overall diagnostic accuracy (> 80%). However, the accuracy of negative diagnosis (exclusion of a certain disease) is slightly higher than this of the positive ones (diagnosis confirmed).