If your doctor suspects that IPF is the cause of your breathing symptoms, he or she will suggest a series of tests that will help determine a definite diagnosis. These may include a chest X-ray, breathing tests or pulmonary function tests (PFTs), bronchoscopy (scope of the lungs) or a surgical procedure called an open lung biopsy. Also, certain other tests such as blood tests, exercise tests or heart tests like an EKG may be suggested to you as being helpful in diagnosing your disease.

Radiologic Tests

The chest X-ray is usually the first test most patients undergo. X-ray beams cannot pass as easily through inflammation and scarred tissue as through normal tissue, so scarring will look more "white" on an X-ray than normal tissue. The most common abnormal finding on the chest X-ray in patients with IPF is a netlike appearance of straight or curved lines with or without small nodules superimposed on the lines. These abnormalities predominantly affect the lower lungs. In addition, the lung volumes are usually smaller as well. However, the conventional chest X-ray is actually a poor test for IPF for several reasons: 1) up to 10% of patients with IPF will have normal chest X-rays; 2) the abnormalities seen are not specific for IPF and, in fact, may look just like pneumonia and many other lung diseases; 3) the abnormalities present are difficult to interpret, with 30% of doctors disagreeing on the interpretation of the same X-ray; and finally, 4) the extent of changes on the chest X-ray does not correlate with the actual severity of the disease. As a result, all patients will require a computed axial tomography (CAT or CT) scan of the chest as well.

Chest X-Ray of IPF showing normal lung at the top and scarring and inflammation at the bottom on both sides.

A CT scan involves lying the patient on a table which slides through a large ring. Although the ring is large in diameter, it is only a couple feet deep. Therefore, the patient’s head may even stick out the other side when getting a CT scan of the chest. An X-ray machine inside the ring rotates very quickly around the patient on the table, taking pictures from every angle. As a result, the patient may have to hold their breath for a few seconds at a time, so that there is no blurring between the picture from above and the picture from below. The whole procedure takes just a few minutes. Then a computer takes all the pictures from all the different angles and puts together a cross-sectional view of the chest with sections about every centimeter.

Diagram of CT Scanner	CT Scanner

To diagnose IPF, a high-resolution CT (HRCT) scan of the chest is often required. From the patient’s perspective, the only difference between an HRCT scan and a conventional CT scan is that they will have to lie both on their back and then on their stomach for a brief time. This is so that the lower back zones of the lung, where most IPF occurs, can be seen better. The computer then puts together cross-sectional views of the chest about every 3mm instead of every centimeter as in the conventional CT scan. As the name implies, these views of the HRCT scan will also be much finer than those of the conventional CT scan. The HRCT scan has a resolution of about 0.5mm. The radiological changes seen in IPF often require this degree of resolution to be seen and separated from those of other lung diseases.

The CT or HRCT abnormalities seen in IPF include the same netlike straight and curved lines seen on conventional chest X-ray. These lines are predominantly seen at the outside edges of the lungs in the lower lung zones. These changes are patchy with areas of normal lung intermingled among abnormal areas. There are also hazy areas of density referred to as "ground glass" because of their appearance. These areas represent the inflammation in the alveoli. The amount of this inflammation, and thus the extent of the ground-glass areas, have been shown to be a key factor in determining prognosis and response to treatment.

Pulmonary Function Tests

Pulmonary function tests (PFTs) measure how well the lungs work. Spirometry is usually the first test. This measures how much air a patient can blow out in one second and also with complete exhalation. This will be decreased if the lungs have a significant amount of fibrosis. As the lung gets progressively more scarred, less air can be drawn into the lungs, and therefore, less air can be blown out. Lung volumes are another set of tests done inside what is called a "body box".

This measures how much total air the lungs can hold. With fibrosis, the lungs may shrink or contract down so that the volumes are smaller. Diffusing capacity is the test which measures how well oxygen moves through the lungs into the bloodstream. Fibrosis will interfere with the diffusion of oxygen, and the diffusing capacity is usually low in persons with IPF. Finally, the last test usually done is a blood gas. Blood is drawn from an artery (the blood vessels which carry blood away from the heart) rather than a vein (the blood vessels which carry blood back to the heart) because arterial blood has just passed through the lungs. Usually the artery in the wrist is used. This blood is analyzed for the oxygen and carbon dioxide levels. The better the lungs function, the more oxygen and less carbon dioxide there is in arterial blood. Pulmonary function tests are quick, easy, and safe to perform and can easily be compared from one physician visit to the next. As a result, they are one of the most commonly used tests for establishing the amount of disease and following its course and response to therapy.

Bronchoscopy

When a doctor finds a patient's pulmonary function tests or chest x-ray is abnormal and characteristic of interstitial lung disease, a biopsy or small sample of lung tissue is often needed in order to make the diagnosis with certainty. This is often done by using a flexible fiberoptic bronchoscope to do a procedure called bronchoscopy. This is done with the patient awake but slightly sedated. The mouth and throat are numbed up or "frozen" with a local anesthetic until all cough and gag reflexes are gone. The doctor then passes this flexible scope through the mouth and into the lungs. A small instrument called a biopsy forceps is then inserted through the scope into the lungs to take several small tissue samples or biopsies. These biopsies are then processed and examined under the microscope.

Bronchoscopy is safe and often times done on an outpatient basis. Because of the small size of samples obtained in this manner, however, a firm diagnosis sometimes cannot be made by the pathology doctors. But because of the ease and safety of this test, and the fact that it may not involve hospitalization and does not require general anesthesia (being totally put to sleep), it is usually considered the best test to begin the diagnostic evaluation of a patient with interstitial lung disease.

Open Lung Biopsy

In situations where a biopsy obtained by bronchoscopy (transbronchial biopsy) is too small for a definite diagnosis to be made, your doctor may advise you to undergo an open-lung biopsy. This involves being admitted to the hospital and undergoing general anesthesia (being put totally to sleep). A chest surgeon then makes an incision between two ribs and removes a section of lung about one-half to three-quarters of an inch long. This is such a small piece of lung tissue that overall lung function is not affected, but it is many times larger than the biopsy obtained by bronchoscopy. In nearly all cases, it is

entirely adequate for a pathologist to make a definite diagnosis. After surgery, patients who have undergone open lung biopsy remain in the hospital for approximately 4-7 days before discharge. In the first few days to weeks following surgery, there is pain around the incision site. Overall, open lung biopsy is a safe procedure, but does involve general anesthesia, hospitalization, and significantly more discomfort and time than bronchoscopy. Therefore, it is used only when a definite diagnosis cannot be established by bronchoscopy.

Pathology

It is important to identify which type of IPF a person has because of the significant differences in treatment and prognosis. The four types of IPF listed in Table 1 are separated best from each other based on their appearance under the microscope, which is why a biopsy is so important. The following pictures demonstrate some of the differences between normal and diseased lung and between the different types of IPF.

Whole lung cross-section

 

Microscopic view of UIP showing the characteristic variation in appearance from one area to another.  There are normal areas at the right and bottom center.  The arrowheads indicate areas of fibrosis or scarring where as the arrow indicates an area of inflammation and fibrosis.		This view of NSIP shows the characteristic diffuse and uniform thickening of the alveolar walls.
This view of DIP shows the characteristic uniform thickening of the alveolar walls as well as filling of the alveoli with inflammatory cells.		This view of AIP shows the characteristic uniform and marked thickening of the alveolar walls by inflammatory cells.

 Bronchoalveolar Lavage

Once a diagnosis of one of the interstitial lung diseases is made, often your doctor will want to attempt to determine if your disease is currently in an active stage (with a high risk of more scar formation in the immediate future) or a non-active stage (with much less risk of further scar formation). IPF can wax and wane with time, and if in a nonactive state, treatment may not be helpful, and only result in side effects. Bronchoalveolar lavage is one test which may help your doctor decide if your disease is active or not. Bronchoalveolar lavage (BAL) is a simple extension of fiberoptic bronchoscopy. Instead of taking a biopsy, saline (salt-water) is injected into a section of lung and then removed immediately by suction. This fluid then contains cells that were contained in the very small air sacs of the lung (alveoli), where the inflammation begins in interstitial lung disease. Whereas transbronchial biopsy samples a section of lung about the size of a pinhead, and open lung biopsy samples a section of lung about the size of your thumbnail, BAL samples fluid from a section of lung about the size of your fist. But BAL differs from the biopsy techniques in that it does not give the kind of information needed to make a specific, definite diagnosis, but gives information regarding whether the disease (in which a diagnosis has already been made by one of the biopsy techniques) is active or not. By sampling a larger section of lung in this way, it can be very informative. At the current time, the number of cells and types of cells obtained by BAL are used by some institutions to make decisions regarding treatment of interstitial lung disease.

BAL is a very safe procedure. Because it does not involve taking pieces of lung tissue but rather injecting and withdrawing fluid, the risk of any serious complication is very low. It is nearly always performed as an outpatient procedure and can be performed multiple times over months or years if necessary without any longlasting adverse effects.

Exercise Testing

Just as patients with interstitial lung disease may have much more shortness of breath when exerting or exercising than when at rest, your doctor may wish to assess your breathing ability and lung function with exercise in addition to the other lung function tests described earlier. This is done usually on a stationary bicycle or a treadmill.

The exact methods used for exercise testing vary from hospital to hospital. Usually though, blood pressure, heart tracing (electrocardiogram) and the blood oxygen level (usually by an electronic clip placed on the ear) are monitored closely, first with minimal exertion and then with progressively greater stress, such as a faster pace on a treadmill or a greater resistance on a stationary bicycle. The test is stopped if your blood oxygen falls, but otherwise is generally continued until you feel you cannot go further. In some instances, your doctor may wish to obtain more detailed information about your heart and lungs with exercise. In that case, in addition to the monitoring mentioned above, you may be asked to breathe into a mouthpiece connected to a computerized lung function machine while you exercise.