Increased amounts of ACE are sometimes secreted by cells found at the margins (outside borders) of granulomas. Granulomas are small tumor-like masses of immune and inflammatory cells and fibrous tissue that create bumps under the skin and throughout the body. They are a classic feature of sarcoidosis, a systemic disorder of unknown cause that often affects the lungs but may also affect many other body organs including the eyes, skin, nerves, liver, and heart. ACE blood levels frequently increase when sarcoidosis-related granulomas develop.
In addition to sarcoidosis, granulomas may be seen with certain infectious conditions, such as leprosy, active histoplasmosis (a fungal respiratory disease), and tuberculosis. They can also develop in occupational settings with chronic exposure to irritant particle poisons such as beryllium, asbestos, and silicon. However, with current worker protections, these causes have become relatively rare.
How is the sample collected for testing?A blood sample is obtained by inserting a needle into a vein in the arm.
Is any test preparation needed to ensure the quality of the sample?No test preparation is needed.
How is it used?ACE is primarily ordered to help diagnose and monitor sarcoidosis. It is often ordered as part of an investigation into the cause of a group of troubling chronic symptoms that may or may not be due to sarcoidosis. ACE will be elevated in 50% to 80% of patients with active sarcoidosis. Concentrations of ACE tend to rise and fall with disease activity. If it is initially elevated in someone with sarcoidosis, ACE can be ordered at regular intervals to monitor the course of the disease and the effectiveness of corticosteroid treatment.
When is it ordered?ACE is ordered when you have signs or symptoms such as granulomas, a chronic cough or shortness of breath, red watery eyes, and/or joint pain that may be due to sarcoidosis or to another disorder. This is especially true if you are between 20 and 40 years of age, when sarcoidosis is most frequently seen. Your doctor may order ACE, along with other tests such as an AFB culture or sputum culture (tests that can detect mycobacterial and fungal infections), when he wants to differentiate between sarcoidosis and another granulomatous condition.
If you have been diagnosed with sarcoidosis and your initial ACE levels were elevated, your doctor may order ACE testing at regular intervals to monitor their change over time.
What does the test result mean?In a diagnostic setting, if ACE levels are high, other diseases have been ruled out, and you have clinical findings consistent with sarcoidosis, then it is likely that you have an active case of sarcoidosis. The finding of a high ACE level helps to confirm the diagnosis. However, sarcoidosis can be present without elevated ACE levels, so a normal ACE level cannot be used to rule out sarcoidosis. Findings of normal ACE levels in sarcoidosis may occur if the disease is in an inactive state, may reflect early detection of sarcoidosis in which the levels of ACE produced are not yet high enough to be abnormal, or may be a case where the cells do not produce increased amounts of ACE. ACE levels are also less likely to be elevated in cases of chronic sarcoidosis.
After diagnosis, ACE levels may be measured to monitor the course of the disease. When initially high levels of ACE are observed to decrease, this usually indicates spontaneous or therapy-induced remission and a favorable prognosis. Rising levels of ACE, on the other hand, may indicate either an early disease process that is progressing or disease activity that is not responding to therapy.
Is there anything else I should know?ACE conversion of angiotensin I to angiotensin II is a normal regulatory process in the body. This process has been targeted by the development of drugs called ACE inhibitors that are commonly used in treating hypertension and diabetes. These drugs inhibit the conversion process, keeping the blood vessels more dilated and the blood pressure lower. ACE inhibitors are useful in managing hypertension, but they are not monitored with ACE blood tests. They may, however, interfere with ACE measurements ordered for other reasons.
- Chronic obstructive pulmonary disease (COPD)
- Cystic fibrosis
- Lung cancer
- Steroid drug therapy
ACE has been found in moderately increased levels in a variety of diseases and disorders such as:
What other tests are used to diagnose sarcoidosis?A variety of tests may be ordered, both to help diagnose sarcoidosis and to determine the degree of organ involvement. Laboratory tests may include a liver panel, CBC, and calcium (blood and urine they tend to be elevated). Other tests may include a physical exam (for skin lesions) pulmonary function tests (about 90% of the time there will be some amount of lung involvement with sarcoidosis), bronchoscopy (passing a flexible tube that is used to look at the lining of the airway and to biopsy the lung), chest x-ray, and gallium screening (radioactive gallium is used to evaluate inflammation). Biopsies of the skin, lungs, lymph nodes, and sometimes liver may also be needed, as may a thorough eye exam. A test called a slit-lamp examination may be used.
What causes sarcoidosis?The cause is not well understood. It is not contagious. It is inflammatory and involves the immune system. It appears to have a genetic component as well as an environmental one. It has been reported both in related and unrelated individuals living in the same area. About 10 40 people per 100,000 are affected in the U.S., the majority of them between 20 and 40 years old. In the U.S. and in the Caribbean, sarcoidosis is more common in those of African descent, but worldwide about 80% of those with sarcoidosis are white. It is relatively common in Scandinavia and Northern Ireland, but rare in China, Japan, and Africa. For some reason, those who have moved from a part of the world where the prevalence is low to a part of the world where it is high tend to take on the risk of the higher prevalence area.