Diagnosis of Sarcoidosis
Blood and Urine Tests
Blood and urine tests are low-risk and minimally invasive ways of evaluating what is happening inside a person. With difficult-to-diagnose diseases like sarcoidosis, these tests can help professionals narrow down the conditions likely to cause reported symptoms. However, although blood and urine tests can help determine the presence of sarcoidosis or similar conditions, neither is sensitive enough to distinguish sarcoidosis from other conditions.
Lung Function Tests
Granulomas in the lungs may cause decreased lung volume, resulting in reduced lung function. Lung function tests, or pulmonary function tests, are used to monitor the progression of sarcoidosis and may also be used to diagnose the condition. These tests assess how well the patient’s lungs are working and are also the best way to monitor the severity of sarcoidosis, so patients are often tested repeatedly over time.
Lung Imaging Tests
Imaging tests may be performed on the lungs to confirm the presence of granulomas or other abnormalities. A chest X-ray is used to detect granulomas in the lungs and lymph nodes. For a more detailed visualization, the physician might prefer a CT scan of the chest. Based on how much inflammation is found in the lymph nodes and lungs, the patient is classified as having stage 1, 2, 3, or 4 sarcoidosis.
Normally, a lung biopsy is recommended if an imaging test, such as an X-ray or CT scan, has revealed an abnormality. A lung biopsy is a procedure to remove a small piece of lung tissue, which is then examined under a microscope to look for abnormalities that could indicate sarcoidosis. This test is more likely to give a definitive diagnostic result.
In rare cases when other tests are inconclusive, the physician might ask for a sample of the lymph nodes found in the chest. This procedure, called a mediastinoscopy, is a minor, minimally invasive surgery that inspects the mediastinal area — the part of the chest cavity between the breastbone and the spinal column, just between the lungs. It is used to check for enlarged lymph nodes in the chest and determine their cause.
If there are bumps and rashes on the skin, a small sample can be taken for pathological analysis of the granulomas. This is called a skin lesion biopsy, which is a very safe procedure that requires numbing only the tissue from where the sample will be taken. Once the sample is removed, it is sent to a laboratory for analysis.