Pulmonary fibrosis (PF) is characterized by scarring, or fibrosis, in the lungs, leading to breathing difficulties, dry cough, muscle aches, and unintended weight loss. Because these symptoms also are present in many other conditions, it can be difficult to correctly diagnose PF.
The diagnostic journey usually starts when a person first notices symptoms and tells their healthcare provider. A doctor then can do some basic tests to see whether PF is a possibility. For example, listening to the lungs with a stethoscope for a characteristic “crackling” sound that may indicate the presence of tissue scarring. Providers typically will examine the patient’s family and medical history to look for potential risk factors, such as a history of smoking, or prior exposure to hazardous substances.
There is no single test to detect PF, however; its diagnosis usually involves a number of tests and a team of specialists working together. A variety of techniques may help in the diagnostic process, as well as in monitoring patients’ overall health status and disease progression following diagnosis.
By taking an X-ray of the chest, specialists can look for signs of lung tissue scarring, which typically present as hazy shadows on a radiograph (the image produced by an X-ray).
A high-resolution computerized tomography (HRCT) scan can produce more detailed images of the lungs, allowing physicians to better determine the extent of lung damage, as well as identify specific patterns of fibrosis, such as honeycombing, which is a common feature of idiopathic pulmonary fibrosis.
An echocardiogram, a test that uses sound waves to produce images of the heart, also may be used to aid in the diagnosis of PF. The presence of scar tissue in the lungs can put pressure on the right ventricle — the right lower chamber of the heart that pumps blood to the lungs — that can be detected by this test.
Lung function tests
Spirometry is a method that involves forcefully breathing into a tube connected to a machine, which can measure how much air is being inhaled and exhaled and how quickly. These values can be used to calculate forced expiratory volume (FEV), which indicates how much air a person can exhale in a forced breath, and forced vital capacity (FVC), which reflects the total amount of air the lungs are able to hold.
Another lung function test, called a gas diffusion study or diffusing capacity of the lung for carbon monoxide (DLCO), can be used to measure how well the lungs are able to transfer oxygen and remove carbon dioxide from the bloodstream.
Notably, some of these tests may be conducted as part of an exercise test, also known as a stress test. In this well-established procedure, patients are monitored while they exercise, typically with a treadmill or a stationary bike. This can let healthcare providers see how lung function changes when the patients is physically active.
Blood tests may be conducted to evaluate the function of the liver and kidneys, and rule out other possible conditions such as infections. Some blood tests can be used to indirectly assess lung function, by measuring how much oxygen is circulating in the bloodstream.
In pulse oximetry, a small device placed on the finger or forehead uses light to measure oxygen saturation — that is, how much of the protein hemoglobin, which red blood cells use to carry oxygen, is actually bound to oxygen. In healthy people, almost all of the hemoglobin is bound to oxygen and oxygen saturation usually is higher than 90%. A lower value may indicate the lungs are not able to transfer oxygen to the bloodstream as well as they should, which can indicate the presence of fibrosis.
In an arterial blood gas test, blood is collected from arteries and then sent to be analyzed for the amount of oxygen, carbon dioxide, and other components. Similar to pulse oximetry, abnormal results from this test may indicate the lungs are not functioning as well as they should.
Bronchoscopy and biopsy
A bronchoscopy allows specialists to look directly at the lungs’ airways and look for signs of scarring or damage. The procedure involves inserting a tube with a small light and camera at the tip down a patient’s windpipe (trachea) through their nose or mouth.
Sometimes during bronchoscopy, a procedure called bronchoalveolar lavage is also performed. This involves flushing a section of the lungs with salt water and then immediately suctioning it out fro analysis.
A biopsy involves taking one or more samples of lung tissue to be analyzed in a lab. Biopsies may be taken during a bronchoscopy, or surgery. Tissue samples obtained during surgery are typically larger and are more likely to allow physicians to make an accurate diagnosis.
Biopsies can be obtained during a thoracotomy, or open chest surgery, as well as in video-assisted thoracoscopic surgery (VATS). During VATS, two or three small incisions are made between the ribs, and the surgery is done using a small camera inserted through the incisions. VATS is considered less invasive than thoracotomy, though both procedures are done under general anesthesia.
Last updated: Sept. 23, 2021
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