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Tests and diagnosis
By Mayo Clinic staff
Few symptoms early on
Sarcoidosis produces few signs and symptoms in its early stages. In some cases, sarcoidosis is diagnosed incidentally based on an X-ray that was taken for other reasons.
When signs and symptoms do occur, they often resemble those of other illnesses. For that reason, your doctor will diagnose sarcoidosis only after ruling out diseases with similar features, such as lymphoma, tuberculosis, rheumatoid arthritis, rheumatic fever and fungal infections.
Even then, doctors can miss sarcoidosis. In the majority of cases, undiagnosed sarcoidosis disappears spontaneously, but a few people go on to develop more-severe signs and symptoms — usually over a period of years.
Commonly used tests
Your doctor will likely use a number of tests to help determine if you have sarcoidosis, how severe it may be and the extent of your treatment. Tests may include:
- Physical exam. Your doctor will likely check for signs of sarcoidosis, such as bumps on your skin, enlarged lymph nodes and redness in your eyes. He or she may also listen for abnormal sounds in your lungs and heart.
- Chest X-ray. Initially, your doctor is likely to order a chest X-ray to check for granulomas or enlarged lymph nodes. Most people with sarcoidosis have an abnormal X-ray. Depending on the results, you may then have one or more follow-up tests.
- Lung function tests. Noninvasive pulmonary function tests measure how much air your lungs can hold and the flow of air in and out of your lungs. They can also measure the amount of gases exchanged across the membrane between your lung wall and capillary membrane. During the tests, you're usually asked to blow into a simple instrument called a spirometer. You're most likely to have pulmonary function tests if you're short of breath or a chest X-ray shows changes in your lungs.
- Blood tests. These are used to check your liver function and the amount of calcium in your blood. For reasons that aren't clear, some people with sarcoidosis have higher than normal blood-calcium levels. Blood tests can also measure a substance called angiotensin-converting enzyme (ACE). Many — but not all — people with sarcoidosis have high levels of ACE, which is produced by the cells that make up granulomas. High ACE levels can also result from other illnesses.
- Bronchoscopy. In this procedure, your doctor uses a thin, flexible tube (bronchoscope) to examine the inside of your air passages and to take a small tissue sample (biopsy) for laboratory analysis. The sample can tell your doctor whether granulomas typical of sarcoidosis (noncaseating granulomas) have formed in your lungs.
- Tissue sample. If parts of your body other than your lungs appear to be affected — your skin, lymph nodes or the outer membrane (conjunctiva) of your eye — your doctor is likely to arrange for a specialist to take a biopsy from these areas. The samples are then examined for noncaseating granulomas. Because these granulomas can result from a number of conditions, their presence alone can't confirm a diagnosis of sarcoidosis. Other subtle infections also can produce granulomas.
- Mediastinoscopy. In some cases, such as if a bronchoscopy test yields no information, your doctor may request a biopsy of lymph nodes from the space between your lungs (mediastinum). If you have sarcoidosis, the disease is likely to have spread to the lymph nodes in your chest cavity even if the nodes aren't enlarged on a chest X-ray or CT scan. A surgeon usually does this procedure using one or more small incisions. Risks of the procedure are small but include bleeding, temporary hoarseness and reaction to the anesthetic.
- Slit-lamp examination. In this exam, your doctor uses a high-intensity lamp to examine the inside of your eyes for damage from sarcoidosis.
- Electrocardiogram (ECG). An electrocardiogram can tell your doctor how well your heart is functioning and whether it may be affected by sarcoidosis. During an ECG, sensors (electrodes) that can detect the electrical activity of your heart are attached to your chest and sometimes to your limbs. An ECG measures the timing and duration of each electrical phase in your heartbeat.
Staging
You may hear your doctor talk about the stage of the disease in your lungs. Staging is usually based on the results of your chest X-rays.
- Stage 0 stands for a normal chest X-ray.
- Stage I involves enlarged lymph nodes only. The lungs themselves look normal.
- Stage II describes enlarged lymph nodes plus abnormalities in the lung tissue.
- Stage III indicates involvement of the lungs only with normal-sized lymph nodes.
- Stage IV involves scarring of lung tissue (pulmonary fibrosis).
All stages require close follow-up, even if not treated at the time. You can have involvement of your liver, skin, heart, eyes or other organs at any stage, even Stage 0.
