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Pulmonary Fibrosis Foundation

Pulmonary Fibrosis Foundation

How PF Is Diagnosed

How PF Is Diagnosed

What is the diagnostic process for PF? The Pulmonary Fibrosis Foundation gives a detailed explanation as part of its Disease Education Webinar Series.


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In its commitment to serving the pulmonary fibrosis (PF) community, the Pulmonary Fibrosis Foundation (PFF) provides a detailed explanation of the process for diagnosing PF.

The roughly 30-minute webinar “The Diagnostic Process for PF” was presented by pulmonologist David J. Lederer, M.D., MS. on October 12, 2018 to help the public understand how doctors identify and diagnose PF.*

Dr. Lederer divides the diagnostic process into several phases: 

  1. Doctor visit clues
  2. Initial diagnostic steps
  3. Establishing disease type

Doctor visit clues

  • Breathlessness. Common symptoms include shortness of breath, which often first appears when exercising or climbing stairs; from walking quickly or frequent phone use as the disease progresses; and eventually with just routine activity and bending over.
  • Cough. Dry cough (no phlegm) is typical, as is post-nasal drip (mucus buildup in the throat).
  • Lung crackles. The Velcro-like sound a doctor will hear when listening to deep breathing with a stethoscope, which can indicate scar tissue and inflammation if the person is not suddenly ill (pneumonia, for instance) and does not have heart disease.

Initial diagnostic steps

If these three major clues are present, a doctor will start thinking about PF and order testing. Two tests are lung function and high-resolution CT scan of the chest, which may be ordered at the same time.

1. Lung function testing can involve multiple tests, but two more common tests are discussed:

a.  Spirometry involves breathing through the mouth into a machine that measures air volume and speed of entry and exit when inhaling and exhaling. This is done during both regular breathing and after taking the deepest breath possible and blowing as hard and as fast as one can. Three important results on a printout are forced vital capacity (FVC), forced expiratory volume in one second (FEV1), and the FEV1/FVC ratio.

i.  “One of the most important measures of disease severity,” FVC is the amount of air blown out after the deepest possible breath, reflecting how much air the lungs can hold. FVC will decrease as scar tissue builds, indicating less lung capacity and greater disease severity. In early disease, a person can have a normal FVC of over 80% of the expected amount for someone the same age and gender with normal lung function.

ii. FEV1 is the amount of air exhaled in the first second of blowing out as hard and as fast as possible, and is often lower than normal in PF. Normal FEV1 is over 80% of the expected amount.

iii. FEV1/FVC ratio is the amount of air exhaled in the first second versus the total amount. Most people with PF have a ratio greater than 70%, where most of the air is exhaled within the first second (FEV1 is usually close to FVC).

b.  Diffusing capacity measures how much air is passing from the lungs into the bloodstream (in other words, the thickness of the lungs’ air sac walls). Diffusing capacity decreases as scarring increases since, even in early disease, it becomes harder to get oxygen into blood with air sac walls getting thicker and stiffer. A normal diffusing capacity is 70%-80% of expected value. (It is usually 30%-40% less than FVC in someone with PF.)

2.  High-resolution computed tomography (HRCT) scans show inside the lungs, where scarring, inflammation and other changes may be seen. Black areas represent normal lung tissue, thick white lines indicate blood vessels, and lighter gray areas (typically near the edges of the lungs) indicate scar tissue. Besides fibrosis, scarring can go by many names such as “reticulation,” “honeycomb” (appearing as such), and “traction bronchiectasis.” The term “ground glass” means haziness, which could indicate inflammation, while “usual pattern of interstitial pneumonia” (UIP) and “non-specific interstitial pneumonia” (NSIP) describe scarring location. Critically, the CT scan confirms the presence of PF.

Establishing disease type—which kind of PF?

Once PF has been established on a CT scan, a doctor will try to find a cause through health and work history plus blood testing. 

PF known causes include:

  • Drugs (example, certain chemotherapies) 
  • Radiation to the chest (cancer treatment)
  • Environmental (called “hypersensitivity pneumonitis” or HP) from exposure to mold and birds, most commonly
  • Autoimmune (“connective tissue disease-related”) in which the immune system attacks the lungs, often occurring with joint inflammation and skin changes such as in rheumatoid arthritis and scleroderma 
  • Occupational (“pneumoconiosis”) from dusts, fibers, and fumes that can cause PF (example, asbestos, coal, silica).

Common diagnostic clues:

  • HP can sometimes be established with known exposures and certain CT scan findings, though a lung biopsy is sometimes needed. 
  • Clues to autoimmune disease-related PF include, for example, stiff, painful joints; rash; dry eyes and mouth; and skin tightening on the face and hands. (A rheumatologist can often confirm without need for lung biopsy.)
  • Occupational clues include job history in mining, quarry work, heavy metals, or asbestos, for example (biopsy is sometimes needed to confirm).

If a cause cannot be found, the disease may be “idiopathic” (of unknown cause)

  • There are many idiopathic subtypes, including IPF (idiopathic pulmonary fibrosis), idiopathic NSIP (non-specific interstitial pneumonia), and sarcoidosis, for example.
    • A CT scan is often enough for diagnosis of IPF if a typical visual pattern of usual interstitial pneumonia (UIP) is present and all other possibilities have been eliminated. 
    • In cases of “probable” UIP, a diagnosis can also usually be made without a lung biopsy, but sometimes it is needed to confirm. (This aligns with new IPF diagnostic guidelines published in 2018.)

Dr. Lederer advises this entire process, or at least the later stages, be done by a pulmonologist. A second opinion can be pursued at any of 68 Pulmonary Fibrosis Foundation Care Centers throughout the U.S.

*Pulmonary Fibrosis Foundation. (2018, October 12). The Diagnostic Process for PF [Webinar]. From PFF Disease Education Webinar Series. https://www.pulmonaryfibrosis.org/patients-caregivers/education-resources/webinars/webinar/2018/10/12/webinar-calendar/the-diagnostic-process-for-pf

The webinar can also be found on the PFF’s YouTube channel to view slides in full screen. Slides are available upon request by contacting the PFF Help Center at help@pulmonaryfibrosis.org.

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