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Updated: Jun 15, 2025
Imaging Features of Systemic Sclerosis-Associated Interstitial Lung Disease
Published on: June 16, 2020
BAL Fluid Cellular Analysis and Radiologic Patterns in Patients With Fibrotic Interstitial Lung Disease
Amanda Grant-Orser1, Michael Asmussen2, Daniel-Costin Marinescu3
1Department of Medicine, University of Calgary, Calgary, AB, Canada; Snyder Institute for Chronic Disease, University of Calgary, Calgary, AB, Canada.
Insights
Bronchial alveolar lavage (BAL) cellular analysis in fibrotic interstitial lung disease (ILD) shows weak correlations with radiologic findings and diagnoses. BAL findings are not reliably associated with imaging features or clinical diagnoses in ILD patients.
Area of Science:
- Pulmonology
- Radiology
- Diagnostic Medicine
Background:
- Bronchial alveolar lavage (BAL) cellular analysis is recommended for diagnosing fibrotic interstitial lung disease (ILD).
- Current data on the clinical utility and correlation of BAL findings with imaging are limited.
- Heterogeneity exists in the interpretation and application of BAL results across centers.
Purpose of the Study:
- To investigate the association between BAL findings and radiologic features, patterns, and clinical diagnoses in patients with fibrotic ILD.
- To assess the correlation of BAL cellularity with high-resolution CT (HRCT) findings.
- To evaluate the utility of BAL in classifying fibrotic ILD patterns.
Main Methods:
- Retrospective review of patients with fibrotic ILD from the Canadian Registry for Pulmonary Fibrosis.
- Standardized multidisciplinary discussion (MDD) for BAL and HRCT interpretation.
- BAL fluid categorized by lymphocyte and neutrophil percentages; HRCT scored for features and patterns.
Main Results:
- BAL cellular analysis was performed in 13% of patients.
- Lymphocyte percentage showed a weak negative correlation with total fibrosis percentage but not with ground glass opacity.
- A mixed BAL pattern was most common; BAL lymphocytosis frequency was similar across HRCT patterns.
Conclusions:
- BAL cellular analyses did not significantly correlate with radiologic features, guideline patterns, or MDD-based diagnoses in fibrotic ILD.
- Ground glass opacities, often considered indicative of inflammation, were not associated with BAL lymphocytosis.
- The clinical utility of BAL cellular analysis in conjunction with imaging for fibrotic ILD diagnosis needs further investigation.
Background:
BAL cellular analysis is often recommended during the initial diagnostic evaluation of fibrotic interstitial lung disease (ILD). Despite recommendation for its use, between-center heterogeneity exists and supportive data concerning the clinical utility and correlation of BAL findings with radiologic features or patterns remain sparse.
Research Question:
In patients with fibrotic ILD, are BAL findings associated with radiologic features, patterns, and clinical diagnoses?
Study Design And Methods:
Patients with fibrotic ILD who underwent BAL for diagnostic evaluation and who were enrolled in the prospective Canadian Registry for Pulmonary Fibrosis were re-reviewed in a standardized multidisciplinary discussion (MDD). BAL was categorized according to guideline-recommended thresholds, and using thresholds of lymphocytosis > 20% and neutrophils > 4.5%. High-resolution CT (HRCT) scans were scored (anonymized to clinical data) for specific features and percentage lung involvement. Radiologists classified HRCT scans according to guideline-defined patterns for idiopathic pulmonary fibrosis and fibrotic hypersensitivity pneumonitis; then, MDD diagnoses were assigned, considering all available data.
Results:
Bronchoscopy with cellular analysis was performed in 209 of 1,593 patients (13%). Lymphocyte % was weakly negatively correlated with total fibrosis % (r = -0.16, P = .023) but not statistically significantly correlated with ground glass opacity % (r = 0.01, P = .94). A mixed BAL pattern was the most frequent in all radiologic patterns (range, 45%-69%), with a minority classifiable according to BAL guidelines. BAL lymphocytosis appeared with similar frequency across HRCT patterns of fibrotic hypersensitivity pneumonitis (21%) and usual interstitial pneumonia (18%). Only 5% of patients with MDD-based fibrotic hypersensitivity pneumonitis had a guideline-defined isolated lymphocytosis > 15%.
Interpretation:
BAL cellular analyses did not significantly correlate with radiologic features, guideline patterns, or MDD-based diagnoses. Ground glass opacities are often interpreted to represent pulmonary inflammation, but were not associated with BAL lymphocytosis in this cohort.
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