Serum angiotensin converting enzyme in respiratory diseases.

More than 1700 estimations of serum angiotensin converting enzyme (SACE) were undertaken, mostly in respiratory disorders, to assess its value as a specific and/or a sensitive indicator of different diseases. Though highest levels were found in lepromatous leprosy consistently, it was also found almost always elevated in active stages of sarcoidosis. Since it is raised in a variety of respiratory disorders, it is not a specific diagnostic test. It is, however, a fairly sensitive index of disease activity in sarcoidosis whether on treatment or not. Sudden elevation, after a prolonged period of low or normal values may indicate relapse in sarcoidosis.