Prognostic Value of Bronchoalveolar Lavage in Systemic Autoimmune Rheumatic Diseases-Associated Interstitial Lung Disease

Background: Systemic autoimmune rheumatic diseases-associated interstitial lung disease (SARD-ILD) presents with varied disease courses, emphasizing the need for reliable predictors of progression. The prognostic utility of bronchoalveolar lavage (BAL) in SARD-ILD remains underexplored. The objective of this study was to evaluate the role of BAL fluid lymphocyte count in predicting disease progression in patients with SARD-ILD. Methods: This observational study included patients with SARD-ILD undergoing BAL as part of their diagnostic workup. Disease progression was defined as either Forced vital capacity (FVC) decrease >10%, two out of the following three criteria within two years: FVC decrease of 5–10%, worsening symptoms, increased fibrosis on imaging, or any of the following: escalation of treatment, Interstitial lung disease (ILD) exacerbation, lung transplantation, or disease-specific mortality. Logistic regression identified predictors of progression. Time-to-progression was assessed using Kaplan–Meier survival curves. The optimal BAL lymphocyte threshold for predicting progression was identified using the Youden Index and the Wilcoxon method. Results: We identified 89 patients, of whom 30 (33.7%) had progressive disease. Progressors had a significantly higher BAL lymphocyte count compared to non-progressors (31.6 ± 24.8% vs. 14.3 ± 16.5%, p < 0.001). BAL lymphocyte proportion was significantly and independently associated with disease progression (odds ratio, 1.05; 95% confidence interval 1.02–1.07; p < 0.01). A lymphocyte count above 9 percent was associated with a markedly increased risk of disease progression (odds ratio, 13.14; 95% confidence interval, 4.20–51.98; p < 0.01). Conclusions: BAL lymphocyte count was associated with a higher likelihood of progression in SARD-ILD. BAL assessment may help identify patients at increased risk of disease progression. However, these findings should be considered exploratory and require validation in larger prospective studies and across individual SARD-ILD subtypes.