Diagnosing Sarcoidosis

Sarcoidosis is caused by chronic and systemic inflammation resulting in the accumulation of small clumps of immune cells called granulomas in several organs.

Diagnosing the disease can be challenging because sarcoidosis’ symptoms vary greatly. Early symptoms are also shared with a number of other disorders, and a diagnostic test able to distinguish sarcoidosis from them does not yet exist. For these reasons, several tests are needed to help physicians exclude other conditions and reach an accurate diagnosis.

Physical examination and medical history

During a physical exam, physicians listen to a patient’s lungs and heart, examine the lymph nodes for swelling, and check for any skin lesions. They may also inquire about complaints such as fever, cough, weight loss, and shortness of breath.

A detailed sharing of your or the patient’s medical history with the physician regarding infections, and certain occupational and environmental exposures also plays an important role in the diagnostic process.

If the physical exam and medical history raises suspicions of sarcoidosis, a differential diagnosis is necessary to help rule out other possibilities. If this also indicates sarcoidosis as a possibility, further testing is needed for confirmation.

Laboratory tests

Although not definitive, minimally invasive blood and urine tests are a useful first step in diagnosing sarcoidosis, and in ruling out other disorders.

Blood tests measure the number of immune cells and certain proteins to assess the level of inflammation in the body. High levels of these markers may indicate an inflammatory condition, such as sarcoidosis.

Blood and urine samples can also detect changes in levels of such molecules as angiotensin-converting enzyme, which is excessively produced by granulomas; alkaline phosphatase, which signals abnormal liver activity; and calcium and creatinine, which indicate poor kidney function.

Elevated calcium levels in the blood and urine are a marker of sarcoidosis, but could also indicate diseases such as cancer or excessive vitamin D or calcium consumption.

As such, while blood and urine tests can help determine the presence of sarcoidosis, neither is sensitive enough to distinguish sarcoidosis from other disorders. To diagnose sarcoidosis with certainty, a further series of tests is likely to be requested.

Imaging scans

The lungs are the most commonly affected organ in people with sarcoidosis. A chest X-ray is used to detect problems in the lungs and surrounding areas, such as inflamed (or enlarged) lymph nodes, the presence of granulomas, or tissue scarring.

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 pulmonary sarcoidosis.

For a more detailed visualization, the physician might prefer a CT scan of the chest. CT scans are becoming a more common diagnostic tool, and may more accurately help assign a stage to the level of pulmonary sarcoidosis in a patient.

On occasion, other imaging tests such as MRI and positron emission tomography (PET) scans may be taken to diagnose sarcoidosis, but these are more commonly used to view organs other than the lungs. Particularly, these scans can be used to assess whether there is any central nervous system, heart, or musculoskeletal involvement.

A Gallium scan or scintigraphy, where a radioactive material is injected into the vein, can provide additional information about inflammation sites in the body.

Lung and skin biopsies

Should an imaging scan suggest a problem, a lung biopsy is normally recommended. The tissue is then examined under a microscope to look for signs that could indicate sarcoidosis.

A bronchoscopy is most commonly used for a lung biopsy; it involves passing a thin and flexible tube — a bronchoscope — through the mouth or nose and down the windpipe. The procedure allows the doctor to see directly into the lungs and to collect small pieces of lung tissue for analyses. However, in some cases, more invasive procedures to collect lung tissue may be needed.

In about one-third of patients, sarcoidosis has some form of skin involvement, typically seen as red nodules, bumps, and plaques. In these cases, a punch biopsy — in which a small circle of skin tissue is removed — is often done. The sample is then analyzed in a laboratory for the presence of granulomas and inflammatory molecules. Punch biopsies can diagnose sarcoidosis in a majority of all cases (an estimated nearly 82% of cases), with few complications.


In rare cases, when other tests are inconclusive, mediastinoscopy can be used for further airway and lymph node inspection. They may be needed to confirm a sarcoidosis diagnosis, as well as to rule out other disorders.

Mediastinoscopy is a minor surgical procedure performed under general anesthesia. It uses a small scope, sometimes with a video camera, to investigate the structures of the chest and upper airways. This scope is inserted into the chest cavity through small incisions made near the collarbone. It can also be used to collect tissues from the lymph nodes that surround the lungs and airways for biopsy.

Lung function tests

Granulomas in the lungs can reduce lung volume, resulting in poorer lung function. As such, a lung function test is commonly given to determine how well the lungs are expanding and supplying tissues systemwide with oxygen.

These tests are used to help diagnose sarcoidosis, and are considered an ideal way to monitor disease severity. As such, patients are often tested repeatedly over time to determine if they need treatment, or how well a given treatment is working.

Other tests

Sarcoidosis can also affect the heart. An electrocardiogram (EKG), which measures the heart’s electrical activity, or an echocardiogram, which uses sound waves to get a picture of the heart’s structures, can be used to assess heart function in sarcoidosis patients.

Sarcoidosis can damage the eyes, even when no symptoms are evident. A thorough eye examination can reveal the presence of inflammation, small granulomas inside the eyelids or on the white of the eye, or damage to the optic nerve.

Liver, kidney, bone marrow, the glands that make tears and saliva, muscles, and other lymph nodes may also be tested if thought necessary.


Last updated: July 26, 2021


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