[Bronchoalveolar lavage findings in patients with diffuse interstitial lung disease: prospective study of a cohort of 562 patients].

OBJECTIVE Study of the bronchoalveolar lavage (BAL) fluid in some interstitial lung diseases can reveal patterns typical to each disease and that can support the diagnosis. The objective of this study was to perform a descriptive analysis of the cytologic study and of the lymphocyte subpopulations in BAL fluid from patients with interstitial lung disease. MATERIAL AND METHODS In this prospective, observational study of 562 patients between January 1991 and January 2005, BAL fluid was analyzed to determine the distribution of cell populations and of lymphocyte subsets: CD3, CD4, CD8, CD3(+)CD4(-)CD8(-), and CD56. RESULTS The mean age was 53.4 years and 53.3% of the patients were women. The following diseases were studied: idiopathic pulmonary fibrosis (n=132), sarcoidosis (n=123), connective tissue diseases (n=133), cryptogenic organizing pneumonia (n=89), and extrinsic allergic alveolitis (n=85). Isolated lymphocytic alveolitis was common in sarcoidosis and extrinsic allergic alveolitis. Mixed alveolitis was the most common pattern in the other interstitial lung diseases. The CD4:CD8 ratio was the most useful parameter. It was high in sarcoidosis (median, 2.3); the ratio was low or inverted in the other interstitial lung diseases, with median values of 1.76 in idiopathic pulmonary fibrosis, 0.45 in extrinsic allergic alveolitis, 0.35 in cryptogenic organizing pneumonia, and 0.33 in the connective tissue diseases. CONCLUSIONS BAL parameters, in association with clinical and radiologic data, help to discriminate between interstitial lung diseases. BAL should therefore be considered a very useful tool in clinical management, particularly when pulmonary biopsy is not conclusive or is not possible.