Which lab tests are used to diagnose idiopathic pulmonary fibrosis?

Updated: Jul 15, 2019
  • Author: Amanda M K Godfrey, MD; Chief Editor: Guy W Soo Hoo, MD, MPH  more...
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Laboratory testing

Results from routine laboratory studies are nonspecific for the diagnosis of idiopathic pulmonary fibrosis. Some tests that may be helpful to exclude other causes of interstitial lung disease include the following:

  • Antinuclear antibodies or rheumatoid factor titers: Positive results in about 30% of patients with IPF, but the titers are generally not high [5] . The presence of high titers may suggest a connective tissue disease

  • C-reactive protein level and erythrocyte sedimentation rate: Elevated but nondiagnostic in idiopathic pulmonary fibrosis

  • Complete blood cell count: polycythemia (rare)

  • Arterial blood gas analysis: chronic hypoxemia (common)

  • Pulmonary function studies: Nonspecific findings of a restrictive ventilatory defect and reduced diffusion capacity for carbon monoxide (DLCO) [6]

A 6-minute walk test (6MWT) is often used in the initial and longitudinal clinical assessment of patients with idiopathic pulmonary fibrosis. In patients who desaturate to less than 88% during a 6MWT, a progressive decline in the DLCO (>15% after 6 mo) is a strong predictor of increased mortality. [7]

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