Diagnostic Utility of Bronchoalveolar Lavage Lymphocytosis in Patients with Interstitial Lung Diseases

Background: Interstitial lung diseases (ILDs) are extremely challenging in terms of diagnosis. Extreme bronchoalveolar lavage (BAL) lymphocytosis is thought to strongly point towards the diagnosis of hypersensitivity pneumonitis (HP). Objectives: Explore the range of different ILD that can present with BAL lymphocytosis, including cases of pronounced lymphocytosis and its diagnostic utility. Methods: Patients with ILD that were subjected to BAL were identified retrospectively from a cohort of consecutive patients. Results: BAL lymphocytosis ≥20% was recorded in 106 patients (27%), while pronounced BAL lymphocytosis ≥40% was recorded in 49 patients (12.5%). The most common diagnoses in patients with BAL lymphocytosis ≥20% and ≥40%, were HP (32.1%), connective tissue disease (CTD)-ILD (26.4%), sarcoidosis (16%), and HP (38.8%), CTD-ILD (24.5%), sarcoidosis (14.3%), respectively. Conclusions: Neither the presence nor the degree of BAL lymphocytosis can point to a specific diagnosis.