Characterising cough and its response to therapy in hypersensitivity pneumonitis

BACKGROUND: Hypersensitivity pneumonitis (HP) is an immune-mediated interstitial lung disease (ILD) driven by repeated antigen exposure in susceptible individuals. Cough is a prominent but poorly characterised symptom, especially in relation to objective measures and treatment response. RESEARCH QUESTION: What are the clinical predictors of cough severity in HP, and how does cough respond to corticosteroid therapy based on subjective and objective assessments? STUDY DESIGN AND METHODS: A prospective cohort of patients with fibrotic HP diagnosed per ATS/JRS/ALAT guidelines was recruited. Baseline assessments included cough visual analogue (VAS) and the Leicester cough Questionnaire (LCQ). Cough frequency was assessed using the VitaloJAK cough monitor in a subset of patients. Multivariable models evaluated predictors of cough severity, and in incident cases, changes in cough outcomes were evaluated after three months of corticosteroid therapy. RESULTS: A total of 101 patients were recruited (41 male; mean age 65 years). The median cough VAS was 35 mm (IQR 14-50 mm) and the median LCQ was 15.2 (IQR 13.2-17.4). The median cough count was 8.7/hr (range 0.2-32.1/hr, n=28). Subjective cough scores correlated with objective cough frequency (cough VAS ρ = 0.69, P < 0.001 and LCQ ρ=-0.555, P = 0.002). Female sex, reduced forced vital capacity (FVC), and higher bronchoalveolar lavage (BAL) lymphocyte fractions were independent predictors of worse cough severity, as measured by cough VAS. Corticosteroids significantly improved cough subjectively (cough VAS -13.7 mm, P = 0.002 and LCQ +1.9, P < 0.001; n = 44) but did not significantly reduce objective cough frequency (n=16). Lung function remained unchanged at three months. INTERPRETATION: Cough is a major symptom for patients with HP. While corticosteroids improved subjective cough, there was no impact on objective cough count. Randomised controlled trials are required to validate these findings and provide evidence for more effective treatments.