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The serum angiotensin converting enzyme test is done to measure how much of this enzyme is in the body. This blood test is done for a variety of reasons, as a way to monitor and diagnose certain medical conditions.
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How this Test is Used
In most cases, this test is used to help monitor or diagnose sarcoidosis, a condition characterized by inflammation (swelling) in the lungs, eyes, skin, lymph nodes, liver, or other tissues. 50 to 80 percent of patients with active sarcoidosis, will have their ACE levels elevated. In order to monitor how well corticosteroid treatment is working and to monitor this disease.
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When is it Ordered?
When a patients has certain signs or symptoms, such as chronic cough, granulomas, shortness of breath, joint pain, and/or watery eyes, this test can be ordered. This symptoms can indicate sarcoidosis, or another condition. Sarcoidosis is most often diagnosed in those between twenty and forty years old. When the health care provider wants to differentiate between another granulomatous condition and sarcoidosis, they may also order other tests along with a serum angiotensin converting enzyme test, such as a sputum culture or AFB culture. Patients who have already been diagnosed with sarcoidosis and had their initial ACE test show their levels were elevated, may have to have this test regularly to keep and eye on their change over time.
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Preparation and Procedure
Some patients will be asked to restrict their consumption of fluids and food for up to twelve hours prior to having this test done. Steroids can reduce ACE levels, so patients on steroid therapy need to talk to their doctors prior to having this test done.
To obtain a sample of the patient's blood, a health care provider will use a vein in the patient's arm. They will insert a needle and collect an adequate amount of blood in a special vial. Some patients experience mild discomfort or stinging when the needle is inserted, but it is rare that this is ever painful. Some patients will have a small bruise after the blood is collected and this is normal and typically goes away in a few days.
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What do the Results Mean?
What is considered a normal result will vary based on the test method used and the patient's age. In typical adults, their ACE levels will be less than 40 micrograms/L. If these levels are increased, it could indicate sarcoidosis, or the following conditions:
- Active histoplasmosis
- Gaucher's disease
- Hodgkin's disease
- Idiopathic pulmonary fibrosis
- Lung cancer
- Primary biliary cirrhosis
- Nephrotic syndrome
- Pulmonary embolism
If these levels are decreased, it could indicate the following:
- Sarcoidosis therapy
- Steroid therapy (most often prednisone)
- Chronic obstructive pulmonary disease
- Cystic fibrosis
- Lung cancer
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Lab Tests Online (2008). ACE. Retrieved on September 8, 2010 from Lab Tests Online: http://www.labtestsonline.org/understanding/analytes/ace/test.html
MedlinePlus. (2009). ACE Levels. Retrieved on September 9, 2010 from MedlinePlus: http://www.nlm.nih.gov/medlineplus/ency/article/003567.htm