Utility of Bronchoalveolar Lavage and Transbronchial Biopsy in Patients with Hypersensitivity Pneumonitis

Making the diagnosis of HP is challenging due to a lack of consensus criteria and variability of both pathologic and radiographic findings. The purpose of this retrospective study was to determine the diagnostic utility of the combination of BAL lymphocyte count and TBBX in patients with HP. We conducted a retrospective cohort study of all patients with a MDD diagnosis of HP at a single center. 155 patients were included in the study. 49% of patients who underwent BAL had a lymphocyte count > 20, 42% had a lymphocyte count > 30, and 34% had lymphocyte count > 40%. The median BAL lymphocyte count was higher in inflammatory HP compared to fibrotic HP. The addition of TBBX to BAL significantly increased the diagnostic yield regardless of the BAL lymphocyte cutoff used. The yield of bronchoscopy with TBBX and BAL when a lymphocyte count > 40% was used as a cutoff was 52%. Our study suggests that the combination of TBBX with BAL significantly increases the likelihood that the procedure will provide adequate additional information to allow a confident MDD diagnosis of HP and may reduce the need for SLB in the diagnostic workup of HP.