What is the approach for evaluating Interstitial Lung Disease (ILD)?

Approach to Evaluating Interstitial Lung Disease (ILD)

The comprehensive evaluation of Interstitial Lung Disease (ILD) requires a systematic approach including high-resolution computed tomography (HRCT), pulmonary function testing, symptom assessment, and in some cases, lung biopsy, with the goal of identifying specific causes and risk factors to guide appropriate management. 1

Initial Assessment

• Evaluate for "velcro" crackles on lung auscultation, which suggest the presence of lung fibrosis and require further investigation 2
• Assess for risk factors including connective tissue diseases (rheumatoid arthritis, systemic sclerosis, polymyositis, dermatomyositis, etc.) 1, 2
• Evaluate for family history of pulmonary fibrosis, which increases risk of ILD progression 1
• Document smoking history, as smoking is associated with increased risk of ILA progression 1, 3
• Inquire about occupational and environmental exposures (vapors, gases, dusts, fumes, air pollution) 1, 2
• Perform baseline symptom assessment, specifically evaluating for cough and dyspnea on exertion 1, 3

Imaging Studies

• HRCT is the primary imaging tool for detecting and characterizing interstitial lung abnormalities 1, 2
• A volumetric HRCT scan should be acquired on full inspiration (slice thickness, 1.5 mm) 2
• Look for specific patterns: ground-glass opacities, reticular abnormalities, traction bronchiectasis, and honeycombing 2, 4
• Classify radiologic findings as non-subpleural, subpleural nonfibrotic, or subpleural fibrotic patterns 4
• For patients with identified interstitial lung abnormalities (ILAs), a follow-up chest CT scan is recommended 2-3 years after baseline, with earlier follow-up (12 months) in certain clinical contexts 1

Pulmonary Function Testing

• Complete pulmonary function tests should include forced vital capacity (FVC), total lung capacity (TLC), and diffusing capacity for carbon monoxide (DLCO) 1, 2
• DLCO is often the earliest physiologic abnormality in ILD 2, 5
• Baseline pulmonary function testing is recommended for all patients with ILAs 1

Laboratory Testing

• Perform autoimmune panel to investigate underlying connective tissue disease, including antinuclear antibodies, rheumatoid factor, anti-CCP, and myositis-specific antibodies 2, 5
• The American Thoracic Society recommends against MUC5B testing and telomere length measurement as initial tests, even in patients with family history of pulmonary fibrosis 1, 2

Additional Diagnostic Procedures

• Bronchoalveolar lavage (BAL) is generally reserved for cases where the first diagnostic impression is inconclusive, or when infection or lung toxicity is suspected 2, 6
• The American Thoracic Society suggests against baseline lung sampling (surgical lung biopsy) for histopathological analysis in patients with ILAs 1
• If tissue is available from procedures performed for other indications (e.g., lung nodule resection), it should be evaluated by histopathology 1

Risk Stratification for ILA Progression

High-risk features for ILA progression include:

• Demographic and clinical factors: family history of pulmonary fibrosis, older age, smoking history, connective tissue disease 1
• Imaging: definite fibrosis on CT (honeycombing, traction bronchiectasis, architectural distortion), subpleural fibrotic patterns, greater extent of abnormalities 1, 4
• Physiologic: abnormal or borderline FVC, TLC, and DLCO 1, 2

Recommended Screening Populations

• Lung cancer screening-eligible population 1
• Patients diagnosed with connective tissue disease 1
• Adults ≥ 50 years of age with a first-degree relative with familial pulmonary fibrosis (FPF) 1

Management Considerations

• Smoking cessation is the single most effective strategy for slowing progression of lung disease 3, 5
• Exposure remediation (environmental, occupational, medication) 1, 3
• Age-appropriate vaccination 1, 3
• For patients with progressive fibrosing ILD, antifibrotic medications like pirfenidone may be considered, as they have shown efficacy in reducing FVC decline in IPF 7

Common Pitfalls to Avoid

• Failing to distinguish between interstitial lung abnormalities (ILAs) and established interstitial lung disease (ILD) 2, 4
• Overlooking the possibility of connective tissue disease in patients presenting with interstitial changes 2, 5
• Relying solely on pulmonary function tests for diagnosis, as they do not have a role in the differential diagnosis of ILD 2, 6
• Not recognizing that not all interstitial markings represent progressive disease; many remain stable for years 8, 4
• Delaying smoking cessation intervention while focusing solely on pharmacologic treatments 3, 5