How to diagnose IPF

How to diagnose IPF

The diagnosis of IPF requires exclusion of known causes, plus radiological and/or histological criteria.1

A multidisciplinary approach to diagnosis involving a pulmonologist, radiologist and pathologist expert in interstitial lung disease has been shown to improve the accuracy of IPF diagnosis.1,9,10

Patients with the key clinical features of IPF should be referred to a pulmonologist who may request a thin-slice HRCT scan without contrast agent after performing pulmonary function tests.

 Diagnostic algorithms

The diagnosis requires exclusion of known causes, plus radiological and/or histological criteria.1

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How to auscultate for IPF 

Lung auscultation is currently the only realistic means to recognise IPF early.10

A key clinical feature for recognising IPF is the presence of Velcro®-like crackles that can be heard when listening to the patient’s lungs. Crackles are discontinuous, short, explosive sounds that, in IPF, resemble the sound of a strip of Velcro® slowly separating.10

When auscultating to investigate the possibility of IPF:10

  • Pay attention to the posterior, basal area of the lungs
  • Listen throughout the entire inspiratory time
  • Crackles are best detected during slow, deep breaths

The crackles are not conclusive of IPF10 and their identification should prompt a pulmonary function test. This may be followed with a thin-slice HRCT scan of the patient’s lungs.

Listen to the sound of IPF

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 Pulmonary function test (PFT)

Identification of fine Velcro®-like crackles during lung auscultation should prompt investigation of lung function via pulmonary function tests to measure:

  •  Spirometry
  •  Diffusing capacity

A restrictive pattern of disease is the most common finding from PFTs in patients with IPF. This restrictive impairment typically manifests as reduced measures of lung capacity and volume, such as forced vital capacity (FVC), total lung capacity (TLC) and residual volume (RV).

These measures may appear normal in IPF patients with a concomitant obstructive disease, such as chronic bronchitis. It is also possible for an IPF sufferer to have a normal PFT while at rest, however, diffusion capacity is usually reduced.

 High-resolution computed tomography

HRCT is an essential part of the diagnostic pathway in IPF because it will detect the pathophysiological changes in lung tissue that cannot be seen on a standard chest X-ray. HRCT has greatly increased the accuracy of IPF diagnosis.1

The extensive fibrosis of lung tissue manifests on an HRCT scan as the presence of reticular shadows and honeycombing.

The thin-slice HRCT must be conducted without contrast, because the contrast agent will conceal the hallmarks of IPF.11

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HRCT scan of IPF lungs