Does bronchoalveolar lavage lymphocytosis predict prognosis in fibrotic hypersensitivity pneumonitis, and is this relationship influenced by low-dose immunomodulatory therapy at the time of BAL?

Background: Bronchoalveolar lavage (BAL) lymphocytosis is associated with improved prognosis in fibrotic hypersensitivity pneumonitis (fHP), although its prognostic value is unclear in patients receiving immunomodulatory treatment. We investigated whether treatment tapered to the lowest tolerated level at the time of BAL modifies associations with disease severity, one-year lung function, and transplant-free survival. Methods: We analysed 247 fHP patients undergoing BAL, including 162 untreated and 85 receiving immunomodulatory therapy at the time of BAL. Associations between BAL lymphocytosis and baseline composite physiologic index (CPI), one-year CPI change, and transplant-free survival were assessed using multivariable flexible parametric survival models incorporating treatment status and interaction terms, adjusted for covariates. Results: Mean age was 63 years, 43% male, 37% ever-smokers. Treated patients at the time of BAL were younger, with more severe disease (higher CPI). Mean BAL lymphocyte percentages were similar between two groups and inversely associated with baseline CPI in both. Higher BAL lymphocyte% were associated with more favourable CPI change in both untreated (-1.7 points per 10% increase; 95%CI -2.5--0.8, Conclusion: BAL lymphocytosis was associated with less severe disease, favourable one-year CPI change and better survival, irrespective of background immunomodulatory therapy.