Objective:

To assess whether immunosuppressive treatment reduced to the lowest tolerated level at the time of bronchoalveolar lavage (BAL) modifies the association between BAL lymphocytosis and disease severity, one-year lung function, and transplant-free survival in fibrotic hypersensitivity pneumonitis (fHP).

Approach:

• Study Design: Analysis of 247 fHP patients undergoing BAL, including 162 untreated and 85 receiving immunomodulatory therapy, assessing associations between BAL lymphocytosis and clinical outcomes.
• Statistical Analysis: Multivariable flexible parametric survival models were used to evaluate the relationship between BAL lymphocyte percentages and clinical outcomes, adjusted for treatment status and covariates.

Key Findings:

• Higher BAL lymphocyte percentages were associated with less severe disease and more favorable one-year changes in composite physiologic index (CPI) in both treated and untreated patients.
• In untreated patients, higher BAL lymphocyte percentages predicted lower mortality (HR 0.87 per 10% increase, p = 0.036).
• In treated patients, higher BAL lymphocyte percentages also predicted lower mortality (HR 0.78, p = 0.025).
• No significant interaction was found between treatment status and BAL lymphocyte percentages regarding mortality or CPI changes.

Interpretation:

BAL lymphocytosis is associated with improved clinical outcomes in fHP, regardless of immunomodulatory therapy.

Limitations:

• The study is observational and may be subject to confounding factors.
• The sample size for histological confirmation of fHP was limited (only 27.5% of patients).

Conclusion:

BAL lymphocytosis is linked to better disease outcomes in fHP, independent of immunomodulatory treatment status.