[Elevated negative predictive value of angiotensin converting enzyme in the diagnosis of active sarcoidosis]

To evaluate the usefulness of angiotensin converting enzyme (ACE) in the differential diagnosis of active sarcoidosis in action with other interstitial and granulomatous processes.

The study involved 30 patients with a histological diagnosis of sarcoidosis, 38 subjects with anatomopathologically and/or microbiologically confirmed pleuropulmonary tuberculosis, and 12 subjects with idiopathic pulmonary fibrosis confirmed by histological studies. Following the technique developed by Rohatgi and Ryan, a radioenzymatic system was used to determine the activity of serum ACE. In patients with sarcoidosis, levels of ACE were measured in active cases as well as those in remission. Our laboratory reference values for those over 20 years of age are 39.84 +/- 9.19 mumol/min/l.

Levels of ACE were significantly higher (p < 0.001) in active sarcoidosis (67.71 +/- 17.73 mumol/min/l) than during inactivity (41.18 +/- 16.00 mumol/min/l), tuberculosis (46.99 +/- 13.65 mumol/min/l), or fibrosis (35.87 +/- 11.36 mumol/mol/l). A cut-off point of 59 mumol/min/l shows a significant association with the diagnosis of active sarcoidosis (p < 0.001) and reaches a negative predictive value of 90.90%.

The usefulness of serum ACE in the differential diagnosis of sarcoidosis should be reconsidered.