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The following is a summary of “Bronchoalveolar Lavage Fluid Cellular Analysis and Radiologic Patterns in Patients with Fibrotic Interstitial Lung Disease,” published in the August 2024 issue of Pulmonology by Grant-Orser et al.

Bronchoalveolar lavage (BAL) cellular analysis is frequently advocated as part of the diagnostic workup for fibrotic interstitial lung disease (ILD). Despite these recommendations, variability in practice exists across centers, and there is a lack of data on the clinical relevance and correlation of BAL findings with radiologic features and patterns. This study investigated whether BAL findings are associated with specific radiologic features, patterns, and clinical diagnoses in patients with fibrotic ILD. Researchers re-evaluated patients from the prospective Canadian Registry for Pulmonary Fibrosis who had undergone BAL as part of their diagnostic assessment. This evaluation was conducted through a standardized multidisciplinary discussion (MDD) and involved categorizing BAL findings based on guideline-recommended thresholds, as well as additional thresholds of lymphocytosis (>20%) and neutrophilia (>4.5%). High-resolution computed tomography (HRCT) scans were independently scored for specific features and percentage lung involvement, with radiologists classifying the HRCTs according to patterns defined for idiopathic pulmonary fibrosis (IPF) and fibrotic hypersensitivity pneumonitis (fHP). 

MDD diagnoses were then assigned based on a comprehensive review of all available data. Out of 1,593 patients, 209 (13%) underwent bronchoscopy with cellular analysis. The analysis revealed a weak negative correlation between BAL lymphocyte percentage and total fibrosis percentage (r=-0.16, p=0.023), while no significant correlation was found with ground-glass opacity percentage (r=0.01, p=0.94). A mixed BAL pattern was predominant across all radiologic patterns, ranging from 45% to 69%, with a minority fitting the guideline-defined BAL criteria. Lymphocytosis was observed with comparable frequency in HRCT patterns of fHP (21%) and usual interstitial pneumonia (UIP) (18%). Only 5% of patients with an MDD-based diagnosis of fHP met the guideline-defined threshold for isolated lymphocytosis (>15%). 

These findings suggest that while BAL analysis is a recommended diagnostic tool, its correlation with specific radiologic patterns and clinical diagnoses in fibrotic ILD may be limited. Further research is needed to clarify the role of BAL in the context of evolving diagnostic and therapeutic strategies for fibrotic ILD.

Source: sciencedirect.com/science/article/abs/pii/S0012369224049304