Diagnosing IPF

Symptoms: Shortness of breath is the most common symptom for IPF. This symptom is minimal at first and often not noticeable. The shortness of breath gradually worsens over months to years, and eventually becomes the most severe symptom. Cough may occur in some individuals although the cough is usually intermittent. Phlegm is unusual except in smokers. Wheezing and coughing blood are rare. The shortness of breath is non-specific and may be due to other lung disorders or non-lung disorders.

Physical Findings: The physician may then hear crackles through the stethoscope. Crackles are a crackling sound or a Velcro-like sound heard. For IPF/UIP, this sound indicates scarring of the lung. These crackles are heard because the scarring near the airways makes hundreds of small "popping" sounds through the stethoscope as the airways open during inspiration.

Radiographic Studies: The combination of shortness of breath and crackles is suggestive of an interstitial lung disease; therefore, a chest x-ray is obtained. The chest x-ray is a useful screening test for the diagnosis of IPF/UIP. Small line shadows, 1 millimeter to 3 millimeters, are seen at the base of each lung. Sometimes, "honeycombing" is seen at the lung bases, which is a cystic pattern that has the appearance of a bee's honeycomb.

These radiographic findings are very suggestive of IPF/UIP. The "high-resolution" chest CT scan (CAT scan) is the most important x-ray test for confirmation of the disease. If this study shows "honeycombing", the diagnosis of pulmonary fibrosis is established. This pattern of pulmonary fibrosis usually represents IPF/UIP. If the amount of fibrosis progresses over time, the diagnosis of UIP is established. Sometimes, in unusual situations, a lung biopsy is needed to establish the definitive diagnosis.

Pulmonary Function Tests: Pulmonary function tests are obtained to confirm the pattern consistent with pulmonary fibrosis, but importantly to determine the severity of the process. These tests are performed in a hospital or clinic laboratory. They take 30 minutes to 1 hour and consists of blowing into a tube, breathing into a tube, sometimes performing a test in an enclosed "body box", and holding the breath for about 10 seconds. There are three important tests.

The first test is the vital capacity, which measures the amount of air in the lungs that can be expelled during a forced expiration and is referred to as the forced vital capacity (FVC). The amount of air is generally 3 to 4 liters. Fibrosis of the lung decreases the vital capacity.

The second test is FEV1, which means forced expired volume in one second. This is the amount of volume expired in one second. A decrease in the ratio of FEV1 to the FVC means airflow obstruction that may occur in asthma or emphysema. There is no airflow obstruction with pulmonary fibrosis so the FEV1/FVC ratio is normal or may even be increased.

The third test is very important for IPF/UIP. This is called diffusion or diffusing capacity. This measures the ability of oxygen to diffuse into the blood. Generally, this happens instantaneously during breathing because there is only one cell lining between the air and the blood. With IPF/UIP, there are many cells and sometimes complete scarring of this area of exchange so that the oxygen partially diffuses into the blood or in some areas does not diffuse into the blood. Therefore, a decreased diffusing capacity indicates severity of the scarring.

This is the most sensitive of the three tests for pulmonary fibrosis and may be moderate to severely decreased even though the vital capacity is normal or slightly decreased. The test is measured in "percent predicted". Mild reduction is from 60% to 80% predicted, moderate reduction is from 40% to 59%, while values less than 40% predicted indicate severe impairment from the scarring.

Oximetry Measurements: The oximeter is often used as a screening test for the amount of oxygen available in the blood hemoglobin. The number is designated as a percent. Oxygen has a very high affinity for hemoglobin and therefore, the hemoglobin is normally fully saturated from 95% to 100%. Pulmonary fibrosis decreases the ability of oxygen to diffuse into the blood and into the hemoglobin, especially during exercise. So the oximetry level is often used as a guide for the current oxygen level. The test is easy to obtain and non-invasive. The test can be used as part of obtaining blood pressure and pulse, and can be used during an exercise program. The hemoglobin desaturates on a log rhythmic basis rather than arithmetic, thus, a few percentage points decrease during the middle of the curve is important. For individuals with IPF, a value of less than 85% is generally used as a need for supplemental oxygen. 

What is a Lung Biopsy?

A lung biopsy is a small piece of lung tissue obtained for microscopic examination and other testing.

What is a VAT Procedure?

There are several methods of obtaining a lung biopsy. Currently, the VAT procedure is preferred. The VAT (Video-Assisted Thoracoscopy) procedure is performed on a day-surgical basis with a one to two day hospital stay. General anesthesia is used. Three incisions are made for the thoracoscopes and a small piece of lung (biopsy) is obtained for staining and review by the pathologist. A small tube is left in the chest to maintain inflation of the lung for 24 to 48 hours. The individual returns home after the procedure.

Can your Family Doctor Treat IPF?

A lung specialist usually evaluates an individual with IPF/UIP for confirmation of the diagnosis and treatment guidance. The family doctor monitors the course of the illness and treatment. For IPF/UIP, intermittent visits to the lung specialist are often needed on an ongoing basis.

As with any medical condition, a second opinion by another lung specialist is an option for confirmation of the diagnosis and review of the management plan. In addition, review of the biopsy by a lung pathologist is also an important option for confirmation of the diagnosis.