What is the recommended diagnostic work‑up and treatment strategy for interstitial lung disease, including idiopathic pulmonary fibrosis and inflammatory interstitial lung disease?

Diagnostic Work-Up and Treatment Strategy for Interstitial Lung Disease

Initial Diagnostic Approach

Begin with high-resolution computed tomography (HRCT) of the chest, which is 91% sensitive and 71% specific for diagnosing ILD subtypes, combined with comprehensive pulmonary function testing including forced vital capacity (FVC), diffusing capacity, and 6-minute walk test with oxygen saturation monitoring. 1

Essential Diagnostic Components

• HRCT imaging is the cornerstone for identifying radiological patterns (usual interstitial pneumonia [UIP], nonspecific interstitial pneumonia, organizing pneumonia) 2, 1
• Pulmonary function testing provides critical prognostic information: a 5% decline in FVC over 12 months is associated with approximately 2-fold increased mortality 1
• Serological testing for autoimmune markers (ANA, RF, anti-CCP, myositis panel, anti-Scl-70) to identify connective tissue disease-associated ILD 2, 3
• Biomarkers including KL-6, SP-D, MMP-7, and CA-125 help predict progressive pulmonary fibrosis risk 4

Tissue Diagnosis When Needed

• Transbronchial lung cryobiopsy is conditionally recommended as an acceptable alternative to surgical lung biopsy in centers with appropriate expertise for IPF diagnosis 2
• Multidisciplinary discussion between pulmonologist, radiologist, and pathologist is mandatory to optimize diagnostic accuracy 2, 5

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Treatment Strategy for Idiopathic Pulmonary Fibrosis

For IPF, initiate antifibrotic therapy with either nintedanib or pirfenidone, which slow annual FVC decline by 44-57%. 2, 1

IPF-Specific Recommendations

• Antifibrotic therapy (nintedanib or pirfenidone) should be started promptly upon diagnosis 2, 1, 6
• Conditionally recommend against antacid medications and antireflux surgery, as recent evidence does not support their use 2
• Avoid glucocorticoids as monotherapy for IPF 2
• Structured exercise therapy reduces dyspnea and improves 6-minute walk distance 1
• Supplemental oxygen for patients who desaturate below 88% on 6-minute walk test improves quality of life 1

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Treatment Strategy for Connective Tissue Disease-Associated ILD

For CTD-ILD, mycophenolate mofetil is the preferred first-line immunomodulatory therapy across all subtypes (systemic sclerosis, rheumatoid arthritis, inflammatory myopathies, Sjögren disease, mixed connective tissue disease). 2, 1, 6

First-Line Therapy Hierarchy by Disease

Systemic Sclerosis-ILD:

• Preferred: Mycophenolate, tocilizumab 2
• Additional options: Rituximab, cyclophosphamide 2
• Strong recommendation against glucocorticoids due to scleroderma renal crisis risk (particularly >15 mg prednisone daily) 2

Rheumatoid Arthritis-ILD:

• Preferred: Mycophenolate 2
• Additional options: Azathioprine, rituximab, JAK inhibitors, tocilizumab, cyclophosphamide 2

Inflammatory Myopathy-ILD:

• Preferred: Mycophenolate 2
• Additional options: Rituximab, azathioprine 2
• Short-term glucocorticoids (≤3 months) conditionally recommended 2

Sjögren Disease-ILD:

• Preferred: Mycophenolate 2
• Additional options: Azathioprine, rituximab, cyclophosphamide 2

Mixed Connective Tissue Disease-ILD:

• Preferred: Mycophenolate 2
• Additional options: Azathioprine, rituximab, cyclophosphamide 2
• Caution with glucocorticoids in patients with SSc phenotype 2

Second-Line Therapy for Progressive Disease

For CTD-ILD progressing despite first-line therapy:

• SSc-ILD: Add nintedanib or consider stem cell/lung transplantation referral 2
• IIM-ILD: Add calcineurin inhibitor, JAK inhibitor, or IVIG 2
• MCTD-ILD: Add IVIG 2

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Progressive Pulmonary Fibrosis (Non-IPF ILD)

For progressive pulmonary fibrosis in ILDs other than IPF, conditionally recommend nintedanib; pirfenidone requires additional research. 2, 1

Defining Progressive Pulmonary Fibrosis

PPF is defined as at least 2 of 3 criteria within the past year with no alternative explanation: 2

• Worsening respiratory symptoms
• Radiological progression on HRCT
• Physiological progression (FVC decline ≥5-10% predicted, or DLCO decline ≥15% predicted)

The incidence of PPF in CTD-ILD is approximately 29% 4

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Rapidly Progressive ILD in Autoimmune Disease

For rapidly progressive ILD (RP-ILD) in systemic autoimmune rheumatic diseases, conditionally recommend pulse intravenous methylprednisolone as first-line therapy. 2

RP-ILD Treatment Options

• First-line agents: Rituximab, cyclophosphamide, IVIG, mycophenolate, calcineurin inhibitors, JAK inhibitors 2
• Upfront combination therapy (double or triple therapy) is conditionally recommended over monotherapy 2
• Triple therapy specifically for confirmed or suspected MDA-5 positive disease 2
• Early lung transplantation referral is conditionally recommended over waiting for progression 2

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Monitoring and Prognostic Considerations

• Serial PFTs every 3-6 months: FVC decline ≥5% over 12 months indicates disease progression and warrants treatment escalation 1, 4
• 6-minute walk test with oxygen saturation monitoring identifies patients needing supplemental oxygen 1
• Biomarker monitoring: Elevated KL-6, SP-D, MMP-7, and CA-125 predict higher PPF risk 4
• SARD-ILD has better prognosis than IPF: 5-year survival approximately 56 months versus 33.6 months, with antisynthetase syndrome and dermatomyositis showing functional improvement rather than decline 7

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Advanced Disease Management

For end-stage ILD, refer for lung transplantation evaluation, which improves median survival from <2 years to 5.2-6.7 years. 1

Additional Considerations for Advanced Disease

• Pulmonary hypertension develops in up to 85% of patients with end-stage fibrotic ILD; inhaled treprostinil improves walking distance and symptoms 1
• Pulmonary rehabilitation improves functional capacity and quality of life across all ILD subtypes 1, 6
• Transplant referral should occur before severe functional decline (FVC <50% predicted or DLCO <40% predicted) 1