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Immunology & Autoimmune
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Currently under review
Pending specialist review and validation.
The angiotensin converting enzyme (ACE) test measures the activity of ACE in your blood. ACE is an enzyme made primarily in the lungs and blood vessel lining that helps regulate blood pressure by converting angiotensin I into angiotensin II. Immune cells called macrophages can also produce ACE in certain inflammatory conditions.
Clinicians often use this test to help evaluate disorders that cause clusters of inflammatory cells, known as granulomas. The result is assessed together with your symptoms, exam findings, and other tests, since ACE levels can be influenced by many factors and are not specific to a single disease.
ACE is commonly used to support the evaluation and monitoring of sarcoidosis, a condition that can affect the lungs, lymph nodes, eyes, skin, and other organs. Levels can reflect inflammatory activity in some people, so your clinician may use the test to follow trends over time along with imaging, eye exams, or lung function testing.
ACE can also be affected by other granulomatous diseases and by non-granulomatous conditions. Some medicines, especially ACE inhibitor drugs used for blood pressure and heart conditions, can lower measured ACE activity. Because of these influences, the test is not diagnostic on its own and is most helpful when interpreted in context.
Your result is compared with your laboratory’s reference interval for your age group. A result outside the reference interval does not by itself confirm or rule out a condition. Higher values may be seen with active granulomatous inflammation in some people, while normal values can occur even when disease is present. Lower values may reflect medication effects or individual variability rather than a health problem.
Doctors often focus on the pattern over time rather than any single value. If your result is unexpected, your clinician may review your medicines, consider repeating the test, or order additional studies such as imaging or eye and lung assessments. Do not start or stop any medication without medical advice.
Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.
Drugs such as lisinopril, enalapril, and ramipril can suppress measured ACE activity, sometimes into the low range. Tell your clinician about all medicines; do not stop therapy unless your clinician advises a plan for testing.
ACE activity tends to be higher in childhood and declines with age. Laboratories provide age-specific reference intervals, so interpretation depends on your age group.
Conditions like sarcoidosis and some infections that form granulomas can increase ACE in some individuals. However, not everyone with these conditions will have elevated ACE, and other disorders may also influence levels.
Improper sample handling, significant hemolysis, or delays in processing can affect enzyme activity measurements. Recent changes in medication timing can also influence results on the day of the blood draw.
Common genetic variants in the ACE gene and individual physiology can affect baseline ACE activity. Pregnancy and some chronic conditions may lower measured ACE independent of disease activity.
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