From the Guidelines
Laboratory tests for interstitial lung disease (ILD) should include pulmonary function tests (PFTs) and high-resolution computed tomography of the chest (HRCT chest) as recommended by the 2023 American College of Rheumatology (ACR)/American College of Chest Physicians (CHEST) guideline 1. The following tests are also indicated for ILD:
- Complete blood count
- Comprehensive metabolic panel
- Erythrocyte sedimentation rate
- C-reactive protein
- Antinuclear antibody
- Rheumatoid factor
- Anti-cyclic citrullinated peptide antibodies
- Anti-neutrophil cytoplasmic antibodies
- Myositis panel (anti-Jo-1, anti-PL-7, anti-PL-12)
- Anti-Scl-70 for scleroderma
- Anti-SSA/Ro and anti-SSB/La for Sjögren's syndrome
- Serum precipitins for hypersensitivity pneumonitis
- Angiotensin-converting enzyme and serum calcium if sarcoidosis is suspected
- Arterial blood gases to reveal hypoxemia, especially with exertion These tests help identify underlying causes of ILD, as many cases are associated with autoimmune conditions or environmental exposures. The pattern of abnormalities can guide diagnosis and treatment planning, though definitive diagnosis often requires integration with clinical presentation, imaging findings, and sometimes lung biopsy. Bronchoalveolar lavage (BAL) cellular analysis may be a useful adjunct in the diagnostic evaluation of individuals who lack a confident usual interstitial pneumonia (UIP) pattern on HRCT imaging of the thorax 1. However, a normal BAL differential cell profile does not exclude microscopic abnormalities in the lung tissue 1. It is essential to consider the degree of uncertainty about the type of ILD, the likelihood that the BAL will provide helpful information, the patient’s cardiopulmonary stability, the presence or absence of a bleeding diathesis, and the patient’s values and preferences when deciding to perform a BAL 1.
From the Research
Laboratory Tests for Interstitial Lung Disease (ILD)
The following laboratory tests are indicated for ILD:
- Complete Blood Count (CBC) parameters, such as neutrophil count, and neutrophil-to-lymphocyte ratio (NLR) 2
- Systemic inflammatory markers, including interleukin (IL)-1, tumor necrosis factor-alpha (TNF-α), matrix metalloproteinase (MMP)-1, MMP-7, galectin (Gal)-3, IL-6, and Krebs von den Lungen-6 (KL-6) 3
- Total antioxidant status (TAS) and total oxidant status (TOS) 3
- Pyruvate kinase (PK) 3
- Ferritin and erythrocyte sedimentation rate (ESR) 3
- C-reactive protein (CRP) 3
- Pulmonary function tests, including forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1) 4, 2
Imaging Tests for ILD
- High-Resolution Computed Tomography (HRCT) is used to assess the extent and severity of ILD 2, 5
- Chest X-ray may be used as an initial screening test, but HRCT is more sensitive and specific for diagnosing ILD 4