What is the workup for a patient with interstitial changes on lung exam?

Workup for Interstitial Changes on Lung Exam

The workup for interstitial changes on lung exam should include high-resolution computed tomography (HRCT), pulmonary function tests (PFTs), and targeted laboratory testing based on suspected etiology, with multidisciplinary assessment for accurate diagnosis and management. 1

Initial Assessment

• Evaluate for "velcro" crackles on lung auscultation, which suggest the presence of lung fibrosis and require further investigation 1
• Document symptoms including dyspnea on exertion and cough, which are present in most patients with interstitial lung disease (ILD) 2
• Assess for risk factors including:
  • Connective tissue diseases (rheumatoid arthritis, systemic sclerosis, polymyositis, dermatomyositis, etc.) 1
  • Family history of pulmonary fibrosis 1
  • Environmental or occupational exposures 2
  • Medication history for potential drug-induced ILD 2

Imaging Studies

• High-resolution computed tomography (HRCT) is the primary imaging tool for detecting and characterizing interstitial lung abnormalities 1

  • A volumetric HRCT scan should be acquired on full inspiration (slice thickness, 1.5 mm) 1
  • Additional acquisitions in ventral decubitus and on expiration (slice thickness, 1 mm; 20-mm interval) should be performed at baseline 1
  • Look for specific patterns: ground-glass opacities, reticular abnormalities, traction bronchiectasis, and honeycombing 1

• Lung ultrasound can be considered as a complementary tool, especially in resource-limited settings 1

  • Use an eight-zone technique to evaluate for B-lines and pleural line abnormalities 1
  • Multiple B-lines in a diffuse and nonhomogeneous distribution indicate interstitial involvement 1

Pulmonary Function Testing

• Complete pulmonary function tests including:
  • Forced vital capacity (FVC) 1
  • Total lung capacity (TLC) 1
  • Diffusing capacity for carbon monoxide (DLCO) - often the earliest physiologic abnormality in ILD 1
  • A 5% decline in FVC over 12 months is associated with approximately 2-fold increase in mortality 2

Laboratory Testing

• Autoimmune panel to investigate underlying connective tissue disease 1
  • Include antinuclear antibodies, rheumatoid factor, anti-CCP, and myositis-specific antibodies 1
• Consider specific biomarkers based on clinical suspicion 1
• Note: MUC5B testing and telomere length measurement are not recommended as initial tests even in patients with family history of pulmonary fibrosis 1

Additional Diagnostic Procedures

• Bronchoalveolar lavage (BAL) is generally reserved for:

  • Cases where the first diagnostic impression is inconclusive 1
  • When infection or lung toxicity is suspected 1
  • To help differentiate between various ILD subtypes 2

• Lung biopsy should be considered when:

  • Diagnosis remains uncertain after non-invasive testing 1
  • Specific histopathologic patterns need to be identified 1
  • Note: In connective tissue disease-associated ILD, lung biopsy is often unnecessary if clinical and radiographic findings are consistent 1

Multidisciplinary Discussion

• Integrate findings from clinical, radiological, and when available, pathological evaluations 1
• Classify the pattern of interstitial lung disease:
  • Usual interstitial pneumonia (UIP) 1
  • Nonspecific interstitial pneumonia (NSIP) 1
  • Hypersensitivity pneumonitis (HP) 1
  • Other patterns specific to underlying conditions 1

Monitoring and Follow-up

• Serial pulmonary function tests to assess disease progression 1
• Follow-up HRCT at intervals determined by the underlying diagnosis and clinical stability 1
• For patients with connective tissue disease and stable pulmonary function, repeat chest HRCT within 12-24 months from baseline 1

Special Considerations

• In patients with connective tissue diseases, a baseline chest CT scan is suggested to screen for interstitial lung abnormalities 1
• For patients with a first-degree relative with familial pulmonary fibrosis, chest CT screening for interstitial lung abnormalities is recommended for adults ≥50 years of age 1
• Consider the possibility of drug-induced interstitial lung disease, especially with medications like mycophenolate mofetil 3

Pitfalls to Avoid

• Failing to distinguish between interstitial lung abnormalities (ILAs) and established interstitial lung disease (ILD) 1, 4
• Overlooking the possibility of connective tissue disease in patients presenting with interstitial changes 1
• Relying solely on pulmonary function tests for diagnosis, as they do not have a role in the differential diagnosis of ILD 1
• Delaying referral to a multidisciplinary team with expertise in ILD, which can lead to misdiagnosis and inappropriate treatment 1