Effect of antigen removal in hypersensitivity pneumonitis

Antigen removal is a cornerstone of treatment of hypersensitivity pneumonitis (HP), but its association with transplant-free survival remains unclear. Further, HP guidelines conflict as to whether antigen removal is a recommended diagnostic test in patients with suspected HP.

The purpose of this study is to (1) evaluate the impact of antigen removal on transplant-free survival and (2) to describe the impact of antigen removal on pulmonary function testing and imaging in a retrospective cohort of patients with HP.

We retrospectively identified HP patients evaluated between 2011 and 2020. Demographic, physiologic, radiographic, and pathologic data were recorded.

212 patients were included in the cohort. Patients who identified and removed antigen had a better transplant-free survival than patients who did not identify antigen and patients who identified but did not remove antigen. Antigen removal was associated with improvement in FVC by 10% predicted in 16.9% of patients with fibrotic HP and 56.7% of patients with nonfibrotic HP.

Our results suggest that over 50% of nonfibrotic HP patients and 16.9% of fibrotic HP patients improve with exposure removal. In addition, antigen removal, rather than antigen identification, is associated with transplant-free survival in HP.