BAL cells analysis and lung function parameters in fibrotic hypersensitivity pneumonitis at baseline and in relation to survival

In fibrotic hypersensitivity pneumonitis, the relevance of bronchoalveolar lavage (BAL) lymphocytosis remains unclear. We investigated the relationship between BAL %lymphocytes, baseline pulmonary function tests (PFTs) and transplant-free survival. We retrospectively analysed 162 treatment-naïve patients (median age 64 years; 43 % male; 39 % ever-smokers) undergoing BAL within three months of PFTs. Mean FVC 79 %, DLCO 43 %, composite physiologic index (CPI) 48. Median BAL lymphocytes were 24 %(IQR 21-28). BAL %lymphocytes were associated with less severe disease, FVC [coefficient 0.28 (95 %C.I. 0.06-0.48), p = 0.01], FEV₁ [0.20(0.0002-0.41), p = 0.05], and CPI [-0.11(-0.21 to -0.01, p = 0.04]. Although BAL% lymphocytes were not correlated with DLCO, significant opposite correlations were observed for its two components: positive with VA% [0.32 (0.18-0.45), p < 0.0005]; negative with KCO% [-0.37(-0.51 to -0.23), p < 0.0005]. In adjusted Cox regression models, BAL %lymphocytes, lower CPI, higher %FVC, %FEV₁ and %DLCO were significantly associated with increased survival. These findings suggest BAL lymphocytosis reflects a pathophysiological pattern linked to better outcomes.