What are the diagnostic criteria for Idiopathic Pulmonary Fibrosis (IPF)?

From the Guidelines

The diagnosis of idiopathic pulmonary fibrosis (IPF) should be made through a multidisciplinary approach combining clinical, radiological, and sometimes histopathological findings, with high-resolution computed tomography (HRCT) of the chest being essential, as recommended by the most recent guidelines 1. To make the diagnosis of IPF, the following steps should be taken:

• Exclude other known causes of interstitial lung disease, including environmental exposures, connective tissue diseases, and drug toxicities
• Perform HRCT of the chest to identify a pattern of usual interstitial pneumonia (UIP), which includes peripheral, basal predominant reticular abnormalities, honeycombing, and minimal ground-glass opacities
• In cases where HRCT findings are not definitive, consider surgical lung biopsy to confirm the diagnosis, showing patchy fibrosis with architectural distortion, fibroblastic foci, and honeycombing
• Use pulmonary function tests to reveal restrictive ventilatory defect with reduced diffusion capacity, and the 6-minute walk test to show exercise desaturation
• Consider bronchoalveolar lavage and transbronchial biopsy to help exclude other conditions, and laboratory tests to include autoimmune markers to rule out connective tissue diseases
• Make the final diagnosis through multidisciplinary discussion involving pulmonologists, radiologists, and pathologists to integrate all findings and ensure accuracy, as early diagnosis allows for timely initiation of antifibrotic therapy with pirfenidone or nintedanib, as recommended by the most recent guidelines 1. The most recent guidelines from 2022 1 provide the most up-to-date recommendations for the diagnosis of IPF, and should be followed to ensure the best possible outcomes for patients. Some key points to consider when making the diagnosis of IPF include:
• The importance of a multidisciplinary approach to diagnosis, as recommended by the guidelines 1
• The use of HRCT to identify a pattern of UIP, which is highly suggestive of IPF, as noted in the guidelines 1
• The consideration of surgical lung biopsy in cases where HRCT findings are not definitive, as recommended by the guidelines 1
• The use of pulmonary function tests and the 6-minute walk test to support the diagnosis, as noted in the guidelines 1
• The importance of excluding other known causes of interstitial lung disease, as recommended by the guidelines 1.

From the Research

Diagnosis of Idiopathic Pulmonary Fibrosis (IPF)

To make a diagnosis of IPF, the following steps can be taken:

• Exclude known causes of pulmonary fibrosis and identify the usual interstitial pneumonia (UIP) pattern of disease either on high-resolution computed tomography (HRCT) scan of the chest or on surgical lung biopsy 2
• Use a multidisciplinary team (MDT) approach, involving pulmonologists, radiologists, and pathologists with expertise in the diagnosis of IPF and other forms of interstitial lung disease 3, 2, 4
• Consider additional investigations, including surgical lung biopsy, in patients with either clinical or CT findings that are indeterminate for IPF 4
• Review the working diagnosis of IPF at regular intervals, as the diagnosis may change 4

Diagnostic Criteria

The diagnostic criteria for IPF include:

• A systematic search of the medical literature and expert opinion of members of the Fleischner Society 4
• A checklist for the clinical evaluation of patients with suspected UIP 4
• The role of CT in permitting diagnosis of IPF without surgical lung biopsy in select cases when CT shows a probable UIP pattern 4

Biomarkers

Novel biomarkers are being explored for the diagnosis of IPF, including:

• Breath and sputum biomarkers 5
• Serologically assessed extracellular matrix neoepitope markers 5
• Oxidative stress biomarkers in lung tissue 5
• Fibroblasts and complete blood count 5 However, there is currently no single biomarker that is specific to IPF 5