The prognostic role of eosinophils in patients with hypersensitivity pneumonitis: a multicenter study

<bold>Introduction:</bold> Complete blood cell count indices have been identified as prognostic biomarkers in patients with interstitial lung diseases. Patients with hypersensitivity pneumonitis (HP) may present with non-specific bronchial hyperresponsiveness, bronchodilator reversibility, eosinophilia or elevated IgE. <bold>Aim:</bold> To investigate the prognostic role of peripheral blood eosinophils in patients with HP. <bold>Methods:</bold> Patients with HP from 8 European centers were prospectively enrolled in the study between from 13/02/2019 to 2/9/2022. <bold>Results:</bold> One-hundred fifteen patients (n=115) were included in the analysis [males: 71 (61.7%), median age 68.0 (95%CI: 65.0 to 70.4), fibrotic HP: 73 (63.5%), non-fibrotic HP: 42 (36.5%)]. Patients with eosinophils≥150/μL presented with significantly higher mortality risk [(HR:2.59 (95%CI: 1.08 to 6.25), p=0.03] and greater FVC% predicted decline in one year [5.00 (95%CI: 2.43 to 6.57) versus -2.00 (95%CI: -8.41 to 1.00), p=0.03] compared to patients with eosinophils<150/μL. Patients with fibrotic HP had significantly higher blood eosinophil count compared to patients with non-fibrotic HP [230 (95%CI:200 to 293) versus 190 (95%CI: 150 to 268), p=0.02]. <bold>Conclusion:</bold> Peripheral blood eosinophils are a prognostic biomarker in patients with HP. Endotyping HP based on eosinophil count may lead to application of anti-eosinophilic therapies commonly applied to severe asthma patients.