Diagnostic value of serum angiotensin converting enzyme activity in lung diseases.

Serum angiotensin converting enzyme (ACE) activity was measured in 10 patients with early active sarcoidosis, nine patients with inactive or resolving sarcoidosis, 10 patients with malignant pulmonary neoplasms, eight patients with miscellaneous lung diseases, and 18 control subjects with no known pulmonary disease. The serum ACE activity, expressed in units/ml, in control subjects (5-88 +/- 1-84), was no different from the values obtained in patients with inactive or resolving sarcoidosis (6-85 +/- 2-48) or miscellaneous lung diseases (4-61 +/- 3-20). However, the ACE activity was found to be markedly raised in patients with early active sarcoidosis (13-49 +/- 2-52), and there was no overlap with control values. The patients with pulmonary neoplasms had significantly lower values of serum ACE activity than the control subjects (2-80 +/- 3-30).