[Increased serum activity of angiotensin-converting enzyme (ACE): indication of sarcoidosis? A 'Bayesian' approach]

Two patients, a man aged 23 and a woman aged 42 years, complained of fatigue and arthralgia respectively. A particularly high serum activity of angiotensin-converting enzyme (ACE) was established during the diagnostic work-up, although sarcoidosis was considered to be unlikely. This led to a series of diagnostic procedures, some invasive, to confirm the diagnosis of sarcoidosis. The diagnosis was not made in either of these patients. The fatigue appeared to be self-limiting and the arthralgia was due to arthrosis. Eventually it was discovered that these patients had a familial elevation of serum ACE activity. The elevation of ACE levels has limited specificity for sarcoidosis (85%) and is therefore of no value in the diagnostic workup, if the a priori probability for sarcoidosis is low.