ACE

This test measures the amount of angiotensin-converting enzyme (ACE) in the blood. ACE is an enzyme produced by endothelial cells to help regulate blood pressure. It catalyzes the conversion of angiotensin I (an inactive protein) to angiotensin II. Angiotensin II functions as a strong vasopressor - it causes arteries to contract, making them temporarily narrower and increasing the pressure of the blood flowing through them. ACE is produced throughout the body, but is especially concentrated in the lungs.

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.

A blood sample is obtained by inserting a needle into a vein in the arm.

No test preparation is needed.