Impact of Antigen Exposure on Outcomes and Treatment Response in Fibrotic Hypersensitivity Pneumonitis

Abstract

Patients with fibrotic hypersensitivity pneumonitis (fHP) are frequently treated with immunosuppression to slow lung function decline; however, the impact of this treatment has not been studied across different types of antigen exposure. In patients with fHP, do disease outcomes and response to treatment vary by antigen type?. A multicenter interstitial lung disease database (XX) was used to identify patients with fHP. The causative antigen was categorized as avian, mold, unknown, or other. Treatment was defined as azathioprine≥ 75mg/d or mycophenolate≥ 1,000mg/d for≥ 30days. Statistical analysis included t tests, χ2 tests, and one-way analysis of variance. Unadjusted and adjusted competing risks and Cox proportional hazards models were used to assess survival. A total of 344 patients were identified with the following causative antigens: avian (n= 93; 27%), mold (n= 88; 26%), other (n= 15; 4%), and unknown (n= 148; 43%). Patient characteristics and lung function were similar among antigen groups with a mean FVC %predicted of 75 ± 20. The percent of patients treated with immunosuppression was similar between antigens with 58%of patients treated. There was no change in lung function or symptom scores with the initiation of immunosuppression in the full cohort. Immunosuppression was not associated with a change in survival for patients with avian or mold antigen (avian: hazard ratio [HR], 0.41; 95%CI, 0.11-1.59; P= 0.20; mold: HR, 1.13; 95%CI, 0.26-4.97; P= 0.88). For patients with unknown causative antigen, survival was worse when treated with immunosuppression (HR, 2.65; 95%CI, 1.01-6.92; P= .047). Response to immunosuppression varies by antigen type in patients with fHP. Additional studies are needed to test the role of immunosuppression in fHP, and particularly in those with an unknown antigen.