What are the laboratory tests for Interstitial Lung Disease (ILD)?

From the Guidelines

Pulmonary function tests (PFTs), including spirometry, lung volumes, and diffusion capacity, are the recommended laboratory tests for interstitial lung disease (ILD) screening and monitoring in people with systemic autoimmune rheumatic diseases, as conditionally recommended by the 2023 American College of Rheumatology (ACR)/American College of Chest Physicians (CHEST) guideline 1. The following tests are suggested for ILD screening and monitoring:

• Pulmonary Function Testing (spirometry; lung volumes and diffusion capacity) in the presence of signs or symptoms of ILD
• High Resolution CT Chest as needed
• Ambulatory Desaturation Testing every 3-12 months Monitoring tests should be performed at the following frequencies:
• Every 3-6 months the 1st year; then less frequently once stable for IM and SSc
• Every 3-12 months the 1st year; then less frequently once stable for RASiDIMCTD These tests help identify the underlying cause of ILD, assess disease severity, and track disease progression and treatment response, with frequency determined by disease severity and treatment regimen 1. Regular monitoring of PFTs is recommended to detect signs of disease progression, such as worsening respiratory symptoms, physiological evidence of progression, and radiological evidence of progressive pulmonary fibrosis (PPF) 1. Signs and symptom assessments, lung function tests, and HRCT are currently used to diagnose and monitor CTD-ILD patients, and impulse oscillometry (IOS) has been identified as an easy alternative to HRCT for detecting early pulmonary involvement in patients with SSc and RA 1.

From the Research

ILD Labs Overview

• Interstitial lung disease (ILD) is a group of pulmonary disorders characterized by inflammation and/or fibrosis of the lung parenchyma, affecting approximately 650,000 people in the US and causing 25,000 to 30,000 deaths per year 2.
• The most common forms of ILD are idiopathic pulmonary fibrosis (IPF), hypersensitivity pneumonitis, and connective tissue disease (CTD) 2.

Diagnosis and Testing

• Thoracic computed tomography is approximately 91% sensitive and 71% specific for diagnosing subtypes of ILDs such as IPF 2.
• Antinuclear antibodies (ANA) are routinely screened in patients with idiopathic interstitial pneumonia, with a prevalence of 32% in ILD patients 3.
• Autoantibody testing, including ANA, rheumatoid factor, and anti-citrullinated cyclic peptide antibody, is recommended for patients undergoing diagnostic evaluation for ILD 4.
• A Delphi survey identified consensus on key steps to facilitate timely diagnosis and treatment of ILD, including primary care evaluation, community pulmonology care, and specialist referral 5.

Treatment and Management

• Antifibrotic therapy with nintedanib or pirfenidone slows annual FVC decline by approximately 44% to 57% in individuals with IPF, scleroderma-associated ILD, and progressive pulmonary fibrosis 2.
• Immunomodulatory therapy, such as tocilizumab, rituximab, and mycophenolate mofetil, may slow decline or improve FVC in patients with connective tissue disease-associated ILD 2.
• Lung transplant may improve symptoms and resolve respiratory failure in patients with end-stage ILD, with a median survival of 5.2 to 6.7 years compared to less than 2 years without transplant 2.
• Exercise training and oxygen therapy can also improve symptoms and quality of life in patients with ILD 2.