The Angiotensin-Converting Enzyme (ACE) serum test provides specific information about an enzyme involved in several bodily functions. This article explains what the ACE test measures, why it is performed, how the procedure unfolds, and what the results can signify.
Understanding Angiotensin-Converting Enzyme
Angiotensin-Converting Enzyme (ACE) is an enzyme primarily found in the lungs and the lining of blood vessels. Its main biological role lies within the renin-angiotensin-aldosterone system (RAAS), a complex hormonal pathway that regulates blood pressure and fluid balance. ACE acts as a catalyst, converting angiotensin I into angiotensin II, a potent molecule that causes blood vessels to narrow. This narrowing, or vasoconstriction, leads to an increase in blood pressure.
ACE also contributes to blood pressure regulation by breaking down bradykinin, a substance that typically relaxes blood vessels. By degrading bradykinin, ACE further supports the body’s mechanisms for increasing blood pressure.
Why an ACE Serum Test is Performed
A healthcare provider orders an ACE serum test to help diagnose and monitor certain medical conditions, primarily sarcoidosis. Sarcoidosis is an inflammatory disease characterized by the formation of small clumps of immune cells, called granulomas, in various organs, particularly the lungs. These granulomas can produce elevated ACE levels, making the test useful for indicating disease activity.
Elevated ACE levels are found in approximately 50% to 80% of individuals with active sarcoidosis. If a person with sarcoidosis has initially high ACE levels, subsequent tests can help monitor disease progression and treatment effectiveness, such as with corticosteroids. While sarcoidosis is the primary reason for this test, elevated ACE levels can also occur in other less common conditions like Gaucher disease, hyperthyroidism, certain liver diseases, and infections such as tuberculosis or leprosy.
How the ACE Test is Conducted
The ACE test involves a routine blood draw, known as venipuncture. A healthcare professional collects the blood sample from a vein in your arm, usually near the elbow or on the back of the hand. They apply a tourniquet to make veins more visible, clean the area with an antiseptic, and then insert a needle to draw blood into a collection tube.
Preparation for an ACE blood test does not typically require fasting. However, inform your healthcare provider about any medications you are taking, as some, like steroid therapy or ACE inhibitors, can influence test results. While needle insertion may cause a brief pinch or sting, the process is quick, usually taking only a few minutes. Minor risks include slight bruising, soreness at the puncture site, or, rarely, feeling lightheaded or faint.
Interpreting Your ACE Test Results
Interpreting ACE test results requires careful consideration by a healthcare professional, as normal ranges vary between laboratories. Typically, a normal ACE level for adults falls between 8 and 52 units per liter (U/L) or is less than 40 micrograms per liter.
Elevated ACE levels often suggest active sarcoidosis, especially when accompanied by other clinical findings. A decrease in previously high ACE levels can indicate sarcoidosis is improving, either spontaneously or due to treatment. However, elevated levels are not exclusive to sarcoidosis and can also point to other conditions.
Conversely, lower-than-normal ACE levels may suggest sarcoidosis is in remission or responding to therapy. Low levels can also be seen in individuals taking ACE inhibitor medications, commonly prescribed for high blood pressure, or in those with chronic kidney disease or hypothyroidism. Your healthcare provider will interpret your specific ACE test results within the context of your overall health, symptoms, and other diagnostic tests.