How Is Sarcoidosis Diagnosed?
The first step in diagnosing sarcoidosis is a thorough evaluation. The inflamed microscopic granulomas seen in the affected organ with sarcoidosis are similar to those in other diseases such as tuberculosis, fungal diseases, berylliosis and farmer's lung. Because of this, a careful evaluation is important to rule out other diagnoses that can look like sarcoidosis. Only after the known causes of granulomas have been ruled out is the diagnosis of sarcoidosis made.
An evaluation to detect sarcoidosis should include the following:
Thorough Medical Examination: This can help rule out other diseases that may be similar to sarcoidosis.
Chest X-ray: Doctors look at chest X-rays for evidence of enlarged lymph nodes and small round spots in the lung caused by the clusters of inflammation. "Staging" can help the doctor determine the degree of lung involvement in sarcoidosis. A scale of 0 – 4 is commonly used, with 4 having the highest amount of lung involvement.
Pulmonary Function Tests: These breathing tests give an indication of the severity of lung disease. There is nothing unique about sarcoidosis on these tests, so they do not substitute for other, more specific tests. Pulmonary function tests can show obstruction of airflow out of the lungs, restriction of the lung's ability to take in air and a decrease in the transport of oxygen from the lung into the bloodstream. The most important types of breathing tests in sarcoidosis are spirometry, lung volumes and diffusing capacity. In some cases, measurement of blood oxygen levels during an exercise test is done.
Tissue Biopsy: A microscopic exam of tissue samples from the lungs or other affected organs is also needed to be sure of the diagnosis and to exclude other causes. A bronchoscopy can obtain this tissue. A bronchoscopy is a procedure in which the doctor places a narrow tube through the nose and into the airways. Sometimes the diagnosis is made by obtaining tissue samples from the skin, liver or enlarged lymph nodes.
Bronchoalveolar Lavage: When a bronchoscopy is done, a small part of lung can be washed (lavaged) in order to obtain some cells of the immune system from the lung. By counting the types of cells in lavage fluid, it is possible to get an estimate of how inflamed the lungs are and whether the type of inflammation is characteristic of sarcoidosis.
Eye Exam: A slit lamp exam by an eye doctor (ophthalmologist) is an important part of an eye exam to detect inflammation.
CT (Computerized Tomography) Scan: A CT scan is a detailed type of X-ray. The CT scan may make it possible to see lymph nodes and scars in the lung when regular chest X-rays sometimes cannot.
Calcium Levels in the Blood and Urine: Regulation of calcium may be disturbed in sarcoidosis. This results in too much calcium in the blood and/or urine. Exposure to the sun, calcium and vitamin D supplements and high dairy intake can stimulate this process. A 24-hour urine sample can measure the calcium level in the urine. A blood sample can be drawn for levels of calcium in the blood. High calcium levels in the blood can be seen with symptoms that may include fatigue, abdominal pain/constipation and mental fogginess. High calcium levels can also lead to kidney dysfunction.
PET (Positron Emission Tomography) Scan: A radioactive labeled sugar is given intravenously. The person is placed in a special scanning machine to see where the radioactive labeled sugar accumulated. Areas of active inflammation take up the radioactive labeled sugar and are detected with the scanning machine. This gives your doctor a better idea of which areas or organs might be involved with sarcoidosis.
Heart Testing: The doctor may order an electrocardiogram (EKG) to evaluate the electrical system of the heart. An echocardiogram may also be done to evaluate the structure and function of the heart. Sometimes, the doctor might order further tests for the heart if there is suspicion of heart involvement with sarcoidosis. These tests might include a Holter monitor and/or a heart MRI (magnetic resonance imaging).