Transbronchial biopsy in chronic hypersensitivity pneumonitis.

Introduction The diagnosis of chronic hypersensitivity pneumonitis (CHP) is based on relevant exposure, tomographic findings and, in some cases, pathological data. The role of bronchoscopy is uncertain, especially in the fibrotic form of CHP. Aim To analyze the yield of transbronchial biopsy (TBBx) in patients with CHP according to tomographic findings and to evaluate the importance of bronchoalveolar lavage (BAL) in the diagnostic approach. Methods This retrospective study analyzed patients with CHP who underwent TBBx in Sao Paulo, Brazil. The TBBx findings were classified as characteristic (granulomas and/or multinucleated giant cells, associated or not with peribronchiolar infiltration of lymphocytes and plasma cells and bronchiolocentric distribution) and supportive (data indicative of small airway injury: peribronchiolar metaplasia, organizing pneumonia, and intra-alveolar foamy macrophages). Results One hundred nine patients were included. The presence of characteristic findings of HP was seen in 16 patients (14.7%), and supportive findings were seen in 32 patients (29.4%), with a total yield of 44%. Pathological characteristic findings were more common in cases without fibrosis on high-resolution computed tomography (HRCT) (27.3% vs. 9.2%, p= 0.014), whereas the presence of supportive findings was more common in fibrotic HP (38.1% vs. 9.1%, p= 0.002). Fifty-two patients had differential cytology in BAL fluid. Lymphocytosis (> 20%) was present in 51.9% of the patients. There was no difference in the median lymphocyte count according to nonfibrotic and fibrotic tomographic findings on HRCT. Conclusion TBBx and BAL fluid cytology have a role in CHP diagnosis.