Clinical Usefulness of Bronchoalveolar Lavage Cellular Analysis and Lymphocyte Subsets in Diffuse Interstitial Lung Diseases

Background: Diffuse interstitial lung diseases (DILDs) form a part of a heterogeneous group of respiratory diseases. Bronchoalveolar lavage (BAL) analysis has been used for differential diagnosis of DILDs, but their clinical usefulness is controversial. The aim of this study was to investigate the clinical usefulness of BAL cellular analysis with lymphocyte subsets for the differential diagnosis of DILDs. Methods: A total of 69 patients diagnosed with DILDs were enrolled. Basic demographic data, BAL cellular analysis with lymphocyte subsets, histology, and high resolution computed tomogram (HRCT) findings were analyzed and compared as per disease subgroup. Results: Significant differences were found between groups in the proportion of neutrophils (P=0.0178), eosinophils (P=0.0003), T cells (P=0.0305), CD4 cells (P=0.0002), CD8 cells (P<0.0001), and CD4/CD8 ratio (P<0.0001). These findings were characteristic features of eosinophilic pneumonia and sarcoidosis. Other parameters were not significantly different between groups. At the cut-off value of 2.16 for sarcoidosis, CD4/CD8 ratio showed sensitivity of 91.7% (95% CI, 61.5-98.6%) and specificity of 84.2% (95% CI, 72.1-92.5%). Conclusions: Routine analysis of BAL lymphocyte subset may not provide any additional benefit for differential diagnosis of DILDs, except for conditions where BAL is specifically indicated, such as eosinophilic pneumonia or sarcoidosis.