How Is Idiopathic Pulmonary Fibrosis Diagnosed?

Idiopathic pulmonary fibrosis (IPF) produces the same kind of scarring and symptoms as some other lung diseases. This makes it hard to diagnose. Seeking medical help, preferably from a pulmonologist (a doctor who specializes in lung problems), as soon as you have symptoms is important.

To diagnose IPF, your doctor will ask about your medical history, perform a physical exam, and do several tests to rule out other causes of your symptoms and learn how badly your lungs are damaged.

Medical History

A complete medical history is important. Your doctor will ask about:

• Your age
• Your history of smoking
• Things in the air at your job or elsewhere that could irritate your lungs
• Your hobbies
• Your history of legal and illegal drug use
• Other medical conditions that you have that can trigger an immune system response
• Your family's medical history
• How long you've had symptoms

Diagnostic Tests

There is no single test for diagnosing IPF. Your doctor will probably conduct several different tests, including the following.

Chest X Ray

A chest x ray takes a picture of your heart and lungs. It can show shadows that suggest scar tissue. Many people with IPF have normal chest x rays at the time they’re diagnosed.

High-Resolution Computerized Tomography

High-resolution computerized tomography (HRCT) scan is an x ray that provides sharper and more detailed images than a regular chest x ray. It can show scar tissue and how much lung damage you have. This test can help your doctor spot IPF at an early stage or rule it out. It also can help your doctor decide how likely you are to respond to treatment.

Lung Function Tests

Your doctor will do a breathing test called spirometry to find out how much lung damage you have. A spirometer is a device that measures how much air you can blow out of your lungs after taking a deep breath. It also measures how fast you can breathe the air out. If there is a lot of scarring in your lungs, you will not be able to move a normal amount of air out of them.

Pulse Oximetry

Your doctor attaches a small device to your finger or earlobe to see how much oxygen is in your bloodstream.

Arterial Blood Gas Test

The doctor takes a small amount of blood from an artery in your arm, usually in your wrist. It’s then checked for oxygen and carbon dioxide levels. This test is a more accurate way to check the level of oxygen in your bloodstream. Your blood can also be tested to see whether you have an infection that may be causing your symptoms.

Skin Test for Tuberculosis

Your doctor injects a small amount of a substance that reacts to tuberculosis (TB) under the top layer of skin on one of your arms. If you have a positive reaction, a small hard lump will develop at the injection site 48 to 72 hours after the test. This test is done to rule out TB.

Exercise Testing

Exercise testing is used to find out how well your lungs move oxygen and carbon dioxide in and out of your bloodstream when you’re active. During this test, you walk or pedal on an exercise machine for a few minutes. Electrodes attached to your chest and an EKG (electrocardiogram) machine show your heart rate, a blood pressure cuff monitors your blood pressure, and a pulse oximeter attached to a finger or ear lobe shows how much oxygen is in your blood.

Sometimes doctors place a catheter in an artery in one of your arms to draw samples of your blood that will provide a more accurate measure of the oxygen and carbon dioxide in it. They may also ask you to breathe into a tube that separates the air you breathe out from room air and provides a precise measure of the amount of oxygen you’ve taken in and carbon dioxide you're breathing out.

Lung Biopsy

Looking at samples of tissue from several places in your lungs under a microscope is the best way for your doctor to diagnose IPF. A lung biopsy can help your doctor rule out other causes of your condition, such as sarcoidosis, cancer, or infection. It can also show your doctor how far your condition has advanced. Doctors use several different procedures to obtain samples of your lung tissue:

• Bronchoscopy. Your doctor inserts a flexible, rubber tube with a tiny light and camera on the end through your nose or mouth into your lungs to look at your airways. He or she then inserts a forceps through the tube to collect tissue to examine. This procedure is usually done under local anesthesia on an outpatient basis.
• Bronchoalveolar lavage. During bronchoscopy, your doctor may inject a small amount of salt water (saline) through the bronchoscope into your lungs. This fluid washes the lungs and helps bring up cells from the area around the air sacs for examination under a microscope.
• Video-assisted thoracoscopy. This is the procedure that doctors use most to obtain lung tissue. Your doctor inserts a small, lighted tube with a camera (endoscope) into your chest through small incisions between your ribs. The endoscope provides a video image of the lungs and allows your doctor to collect samples of tissue. This procedure must be done in the hospital, under general anesthesia.
• Thoracotomy. Your doctor removes a few small pieces of lung tissue through an incision in the chest wall between your ribs. Thoracotomy is done in the hospital under general anesthesia.