Diagnosis of sarcoidosis can be difficult as the symptoms and laboratory findings associated with it can occur in many other diseases. Currently, there is no singular test that can diagnose it. Your doctor will take a complete medical history (including occupational history, medication history and environmental exposures), do physical and recommend tests if sarcoidosis is suspected.
Some of the tests that may be done to help diagnose sarcoidosis include:
Chest X-rays: The X-ray picture of chest shows lungs, heart and surrounding lymph nodes. It can show the extent of involvement of the lung by the disease. Your doctor can assess the severity of the disease based on the chest X-ray.
Bronchoscopy: This test helps to look at the insides of the airways. A special instrument with a small fiberoptic camera is passed through trachea (windpipe) to look into bronchial tubes (airways) of the lungs. This permits your doctor to examine the inside of your airways and take a biopsy (a small tissue sample) to look for granulomas and to rule out infection. It is a commonly performed as a safe, low risk and outpatient procedure, which can help your doctors to make an accurate diagnosis. Before doing the procedure, medications will be given to you to help you relax as these can make you groggy. The procedure usually lasts 15 to 45 minutes, but you will need several hours to recover.
CT scan: CT scan (computed tomography scan) is a painless and non-invasive test, which takes a series of detailed pictures of the part of the body that is being examined. It provides better details of the lungs and lymph glands than a chest X-ray.
Mediastinoscopy: This surgical procedure is done to take biopsy of lymph nodes in the chest cavity. An instrument is passed through a small incision at the base of the neck to the chest. Now-a-days, mediastinoscopy is not done often as the bronchoscopy-guided biopsies have become widespread.
Pulmonary function (breathing) tests: The test determines how well your lungs are working (expanding and exchanging oxygen and carbon dioxide in the blood). One pulmonary function test uses a device called a spirometer. This measures how fast air goes in and out of the lungs. Formation of granulomas and fibrosis of the lung tissue causes the lung to become stiff and makes it more difficult for the lungs to expand and exchange gases.
Biopsies: Apart from taking biopsy while doing bronchoscopy or lymph node biopsy by mediastinoscopy, your doctor may take tissue samples from any other involved tissue or organs such as other lymph nodes, skin etc to see if granulomas are present. Biopsy examination of the tissue may show granulomas (abnormal masses or nodules consisting of inflamed tissue) in one or more of the major organs of the body. As granulomas can form in many other diseases, finding granuloma is not diagnostic of sarcoidosis.
These are some tests that may be done if you have signs and symptoms suggestive of sarcoidosis. Other tests that may be done include blood tests (such as angiotensin-converting enzyme (ACE) levels, calcium levels and liver function tests), pulse oximetry, electrocardiogram (EKG or ECG), PET scan and slit-lamp examination.