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Sarcoidosis (cont.)

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What do laboratory tests show?

No single test can be relied on for a correct diagnosis of sarcoidosis. X-rays and blood tests are usually the first procedures the doctor will order. Pulmonary function tests often provide clues to diagnosis. Other tests may also be used, some more often than others.

Many of the tests that the doctor calls on to help diagnose sarcoidosis can also help the doctor follow the progress of the disease and determine whether the sarcoidosis is getting better or worse.

Chest X-ray

The chest X-ray is often helpful to give the doctor a picture of the lungs, heart, as well as the surrounding tissues containing lymph nodes (where infection-fighting white blood cells form) and give the first indication of sarcoidosis. For example, a swelling of the lymph glands between the two lungs can show up on an X-ray. An X-ray can also show which areas of the lung are affected.

Pulmonary function test

By performing a variety of tests called pulmonary function tests (PFT), the doctor can find out how well the lungs are doing their job of expanding and exchanging oxygen and carbon dioxide with the blood. The lungs of sarcoidosis patients cannot handle these tasks as well as they should; this is because granulomas and fibrosis of lung tissue decrease lung capacity and disturb the normal flow of gases between the lungs and the blood. One PFT procedure calls for the patient to breathe into a machine, called a spirometer. It is a mechanical device that records changes in the lung size as air is inhaled and exhaled, as well as the time it takes the patient to do this.

Blood test

Blood analyses can evaluate the number and types of blood cells in the body and how well the cells are functioning. They can also measure the levels of various blood proteins known to be involved in immunological activities, and they can show increases in serum calcium levels and abnormal liver function that often accompany sarcoidosis.

Blood tests can measure a blood substance called angiotensin converting enzyme (ACE). Because the cells that make up granulomas secrete large amounts of ACE, the enzyme levels are often high in patients with sarcoidosis. ACE levels, however, are not always high in sarcoidosis patients, and increased ACE levels can also occur in other illnesses.

Bronchoalveolar lavage

This uses an instrument called a bronchoscope - a long, narrow tube with a light at the end - to wash out, or lavage, cells and other materials from inside the lungs. This wash fluid is then examined for the amount of various cells and other substances that reflect inflammation and immune activity in the lungs. A high number of white blood cells in this fluid usually indicate an inflammation in the lungs.

Biopsy

Microscopic examination of specimens of lung tissue obtained with a bronchoscope, or of specimens of other tissues, can tell a doctor where granulomas have formed in the body and can provide the ultimate diagnosis.

Gallium scanning

In this procedure, the doctor injects the radioactive chemical element gallium-67 into the patient's vein. The gallium collects at places in the body affected by sarcoidosis and other inflammatory conditions. Two days after the injection, the body is scanned for radioactivity. Increases in gallium uptake at any site in the body indicate that inflammatory activity has developed at the site and give an idea of which tissue, and how much tissue, has been affected. However, since any type of inflammation causes gallium uptake, a positive gallium scan does not necessarily mean that the patient has sarcoidosis.

Kveim test

This test involves injecting a standardized preparation of sarcoid tissue material into the skin. On the one hand, a unique lump formed at the point of injection is considered positive for sarcoidosis. On the other hand, the test result is not always positive even if the patient has sarcoidosis.

The Kveim test is not used often in the United States because no test material has been approved for sale by the U.S. Food and Drug Administration. However, a few hospitals and clinics may have some standardized test preparation prepared privately for their own use.

Slit-lamp examination

An instrument called a slit lamp, which permits examination of the inside of the eye, can be used to detect silent damage from sarcoidosis.

Medically Reviewed by a Doctor on 11/20/2013

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Source: MedicineNet.com
http://www.medicinenet.com/sarcoidosis/article.htm

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