In predisposed individuals, hypersensitivity pneumonitis (HP) is a collective noun for a group of diffuse lung diseases characterized by some degree of bronchiolar and interstitial granulomatous inflammation caused by persistent inhalation exposure and subsequent immune sensitization to a large potential diversity of (predominantly) organic antigens. Forceps transbronchial lung biopsy (TBLB) and bronchoalveolar lavage have historically been conducted on a case-by-case basis in suspected cases of HP. Researchers wanted to see how conventional TBLB contributed to the integrated multidisciplinary diagnosis of an HP patient group. In 50.0 percent of the cases submitted to TBLB, the biopsies revealed representative material with histologic characteristics that contributed to the diagnostic debate in some way. In patients where TBLBs were not performed or the results were found to be devoid of significant findings, 73.1 percent were still diagnosed as HP on the basis of other diagnostic elements, without the need for surgical video-assisted thoracoscopic lung biopsy/transbronchial lung cryobiopsy; 15.4 percent of patients were diagnosed with HP after a VATS/TBLCB procedure.

Finally, about 11.5 percent of patients were judged to be an unacceptable risk for VATS/TBLCB but obtained a multidisciplinary provisional diagnosis with a fair level of confidence based on clinical, radiologic, and immunologic features. Despite its limitations, TBLB can nevertheless play a role in the diagnostic workup of HP, especially in acute/inflammatory HP, providing definitive or supporting histologic information for multidisciplinary discussion in up to 50% of patients.

Reference:https://journals.lww.com/clinpulm/Fulltext/2020/11000/The_Diagnosis_of_Hypersensitivity_Pneumonitis_and.6.aspx