The Angiotensin-Converting Enzyme (ACE) test is a common medical diagnostic tool. This blood test measures the levels of a specific enzyme in the body, providing healthcare professionals with valuable information. Understanding this test involves learning what the enzyme does, why the test is performed, how to interpret its results, and what the procedure entails.
What ACE Stands For and Its Role
Angiotensin-Converting Enzyme (ACE) is a protein primarily produced by endothelial cells lining blood vessels, especially in the lungs. ACE plays a significant role in the body’s Renin-Angiotensin-Aldosterone System (RAAS), a complex hormonal system that regulates blood pressure and fluid balance.
Within the RAAS, ACE acts as a catalyst, converting angiotensin I into angiotensin II. Angiotensin II is a potent molecule that causes blood vessels to narrow, increasing blood pressure. Additionally, ACE contributes to blood pressure regulation by breaking down bradykinin, a substance that promotes vasodilation, or the widening of blood vessels.
Why the ACE Test is Performed
Healthcare providers primarily order an ACE test to assist in the diagnosis and monitoring of sarcoidosis. Sarcoidosis is an inflammatory condition characterized by the formation of small clusters of immune and inflammatory cells, called granulomas, in various organs. These granulomas can produce increased ACE, elevating the enzyme’s level in the bloodstream.
The test helps determine sarcoidosis severity and treatment effectiveness. Elevated ACE levels are found in 50% to 80% of individuals with active sarcoidosis, making it a marker of disease activity. Monitoring these levels over time can provide insights into disease progression or remission.
While sarcoidosis is the main condition for which an ACE test is performed, elevated ACE levels may also be relevant in other conditions, including Gaucher disease, an inherited metabolic disorder, leprosy, tuberculosis, hyperthyroidism, diabetes, and certain liver diseases. The ACE test is a helpful diagnostic tool, but it is used in conjunction with other clinical findings and tests to confirm a diagnosis.
Understanding Your ACE Test Results
Interpreting ACE test results involves considering the measured level against established reference ranges, which can vary between laboratories. For adults, a normal range for ACE levels is often between 8 and 52 U/L (units per liter) or less than 40 micrograms per liter. Children and adolescents often have naturally higher ACE levels compared to adults.
Elevated ACE levels most commonly suggest active sarcoidosis, especially when combined with other symptoms and diagnostic findings. In individuals with sarcoidosis, a rise in ACE levels can indicate worsening disease activity, while a decrease may signify improvement, either due to treatment or spontaneous remission.
Conversely, lower-than-normal ACE levels are less common and can indicate different scenarios. Low levels might be observed in individuals undergoing steroid therapy for sarcoidosis, suggesting treatment effectiveness. Certain medications, particularly ACE inhibitors prescribed for high blood pressure or heart conditions, can also lead to decreased ACE levels. Additionally, chronic kidney disease, chronic liver disease, and hypothyroidism are sometimes associated with lower ACE levels. A healthcare professional must interpret ACE test results within the context of a patient’s overall medical history, symptoms, and other laboratory or imaging findings.
What to Expect During the ACE Test
The ACE test is a straightforward blood draw procedure, similar to many routine blood tests. A healthcare professional, often a phlebotomist, collects a blood sample from a vein, typically located in the arm, such as the inside of the elbow or the back of the hand. A tourniquet may be placed around the upper arm to make the vein more visible. After cleaning the skin, a sterile needle is inserted to collect blood into a tube or vial. Most individuals experience only a slight prick or stinging sensation, and the collection process is usually quick, taking only a few minutes.
Preparation for an ACE test is generally minimal, and fasting is often not required. However, always follow specific instructions from your healthcare provider or laboratory, as concurrent tests might require fasting. Inform your doctor about any medications, especially blood thinners or ACE inhibitors, as these can affect results or require precautions.
After the blood draw, a cotton ball or gauze is placed over the puncture site with light pressure to stop bleeding. Minor throbbing or slight bruising is possible but typically resolves quickly.