From the Guidelines
The workup for interstitial pneumonitis should begin with a thorough history and physical examination, followed by high-resolution computed tomography (HRCT) of the chest and pulmonary function tests (PFTs) with diffusion capacity measurement, as recommended by the most recent guidelines 1.
Initial Evaluation
The initial evaluation of patients with suspected interstitial lung disease (ILD) should include a complete history and physical examination, with a search for clinical features suggestive of connective tissue disease (CTD) 1. The presence of 'velcro' crackles in lung auscultation suggests the presence of lung fibrosis and should be addressed and considered if present.
Laboratory Studies
Laboratory studies should include:
- Complete blood count
- Comprehensive metabolic panel
- Erythrocyte sedimentation rate
- C-reactive protein
- Antinuclear antibodies
- Rheumatoid factor
- Anti-cyclic citrullinated peptide antibodies to evaluate for underlying connective tissue diseases
- Specific antibody panels for hypersensitivity pneumonitis should be ordered if environmental exposures are suspected
Imaging Studies
High-resolution computed tomography (HRCT) is the primary imaging tool used to detect ILD and outline its extension and pattern 1. A volumetric HRCT scan should be acquired on full inspiration, complemented at baseline with an additional acquisition in ventral decubitus and a non-contiguous acquisition on expiration.
Pulmonary Function Tests
Pulmonary function tests (PFTs) are a reliable tool for early ILD detection and provide the most accurate measurement of disease severity 1. Detection of decreased diffusing capacity for carbon monoxide (DLCO) can aid an early diagnosis.
Bronchoscopy and Lung Biopsy
Bronchoscopy with bronchoalveolar lavage can help identify infectious causes and cellular patterns, while transbronchial or surgical lung biopsy may be necessary for definitive diagnosis in unclear cases, as suggested by earlier guidelines 1.
Multidisciplinary Discussion
Pulmonologists often use multidisciplinary discussion involving radiologists and pathologists to reach a final diagnosis, which is essential because interstitial pneumonitis encompasses various conditions with different treatments and prognoses, ranging from idiopathic pulmonary fibrosis to hypersensitivity pneumonitis to drug-induced interstitial lung disease. Early diagnosis is crucial as some forms respond well to immunosuppression with corticosteroids or steroid-sparing agents, while others may require antifibrotic therapy or removal of an offending agent.
From the Research
Interstitial Pneumonitis Workup
- The workup for interstitial pneumonitis typically involves a combination of clinical evaluation, imaging studies, and physiologic assessment 2.
- Thoracic computed tomography is approximately 91% sensitive and 71% specific for diagnosing subtypes of interstitial lung diseases (ILDs) such as idiopathic pulmonary fibrosis (IPF) 2.
- Physiologic assessment, including forced vital capacity (FVC) and 6-minute walk test, provides important prognostic information and can help guide treatment decisions 2, 3.
- Autoantibody testing, including anti-nuclear antibodies, rheumatoid factor, and anti-citrullinated cyclic peptide antibody, may be useful in identifying patients with connective tissue disease-associated ILD 4, 5.
Diagnostic Criteria
- The European Respiratory Society/American Thoracic Society Task Force has proposed criteria for interstitial pneumonia with autoimmune features (IPAF), which includes a combination of clinical, serologic, and histopathologic findings 5.
- The IPAF criteria include the presence of interstitial pneumonia on high-resolution computed tomography, positive autoantibody tests, and/or histopathologic findings consistent with autoimmune disease 5.
Treatment Options
- Treatment for interstitial pneumonitis depends on the underlying cause and severity of disease, and may include antifibrotic therapy, immunomodulatory therapy, oxygen therapy, and lung transplantation 2, 3.
- Antifibrotic therapy with nintedanib or pirfenidone has been shown to slow disease progression in patients with IPF and other forms of ILD 2.
- Immunomodulatory therapy, such as tocilizumab, rituximab, and mycophenolate mofetil, may be effective in patients with connective tissue disease-associated ILD 2, 4.