How is idiopathic pulmonary fibrosis (IPF) diagnosed?

Updated: Aug 06, 2018
  • Author: Ali Nawaz Khan, MBBS, FRCS, FRCP, FRCR; Chief Editor: Eugene C Lin, MD  more...
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Answer

Answer

The diagnosis of IPF is made on the basis of the patient's history, clinical findings, pulmonary physiology, and imaging results. The diagnosis is one of exclusion. Nonidiopathic causes must be excluded first because of the important therapeutic implications. After nonidiopathic causes are excluded, further investigation of patients with IPF typically reveals radiographic abnormalities and restrictive lung physiology with decreased diffusion capacity. [2, 3, 4]

Plain chest radiography is usually the first investigation performed for patients with suspected interstitial lung disease. However, the findings on conventional radiography are highly nonspecific.

High-resolution computed tomography (HRCT) scanning defines the underlying lung parenchymal abnormalities better than plain radiography. [5, 6]  Studies have shown that HRCT may obviate surgical lung biopsy in some patients. Raghu et al compared the diagnostic accuracy of clinical evaluation in combination with HRCT with the accuracy of histology of surgical lung-biopsy samples. [7] Clinical assessment in conjunction with careful review of HRCT scans was 60% sensitive and 97% specific for IPF. However, although HRCT may obviate the need for tissue diagnosis in 60% of patients, surgical lung biopsy is still needed in 40%.

For diagnoses other than IPF, a combination of clinical assessment and HRCT is neither sensitive nor specific enough to be relied on without surgical biopsy. Open lung biopsy remains the criterion standard. In immunocompetent patients, the benefit is relatively low because corticosteroid therapy is frequently administered after biopsy. In immunocompromised patients, approaches to therapy change substantially after tissue confirmation, but mortality is high. Therefore, open biopsy should be performed only in patients in whom the diagnosis is likely to change therapy and in patients who have a reasonable prognosis.

Radionuclide scanning with gallium-67 may depict interstitial fibrosis and may show changes early. This feature may be of therapeutic benefit, but the changes are nonspecific and do not remove the need for lung biopsy.


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