Simple Radioassay for Measuring Serum Activity of Angiotensin-Converting Enzyme in Sarcoidosis

Abstract

Using a new simple radioassay, which has some advantages over the spectrophotometric and spectrofluorometric methods, we found the serum activity of angiotensin-converting enzyme in 62 normal subjects and 60 patients with various nonsarcoid pleuropulmonary diseases to be 90.7 ± 23.4 mU/ml (mean ± SD) and 84.6 ± 28.5 mU/ml, respectively. Taking an activity of 137.5 mU/ml (mean ± 2 SD) as the highest limit of normal, we found the frequency of false-positive results was two of 62 in normal subjects and five of 60 in various nonsarcoid pulmonary diseases. The serum activity of angiotensin-converting enzyme in 40 patients with active sarcoidosis was 177.7 ± 59.7 mU/ml, which was significantly elevated (P <0.0005) compared to the two previously mentioned groups, as well as to eight patients with stable sarcoidosis (111.0 ± 26.0 mU/ml) and seven patients who had recovered from sarcoidosis (78.0 ± 11.6 mU/ml). Five of the six patients with active sarcoidosis who had normal serum activity of angiotensin-converting enzyme had stage 1 disease of less than two years’ duration with no extrathoracic involvement. In all 18 patients with active sarcoidosis who received prednisone, the serum activity of angiotensin-converting enzyme returned to normal and was associated with symptomatic and objective clinical improvement We suggest that the serum activity of angiotensin-converting enzyme is helpful in diagnosing and assessing the activity of sarcoidosis and that serial determinations may be helpful in monitoring the dosage and duration of corticosteroid therapy. Using a new simple radioassay, which has some advantages over the spectrophotometric and spectrofluorometric methods, we found the serum activity of angiotensin-converting enzyme in 62 normal subjects and 60 patients with various nonsarcoid pleuropulmonary diseases to be 90.7 ± 23.4 mU/ml (mean ± SD) and 84.6 ± 28.5 mU/ml, respectively. Taking an activity of 137.5 mU/ml (mean ± 2 SD) as the highest limit of normal, we found the frequency of false-positive results was two of 62 in normal subjects and five of 60 in various nonsarcoid pulmonary diseases. The serum activity of angiotensin-converting enzyme in 40 patients with active sarcoidosis was 177.7 ± 59.7 mU/ml, which was significantly elevated (P <0.0005) compared to the two previously mentioned groups, as well as to eight patients with stable sarcoidosis (111.0 ± 26.0 mU/ml) and seven patients who had recovered from sarcoidosis (78.0 ± 11.6 mU/ml). Five of the six patients with active sarcoidosis who had normal serum activity of angiotensin-converting enzyme had stage 1 disease of less than two years’ duration with no extrathoracic involvement. In all 18 patients with active sarcoidosis who received prednisone, the serum activity of angiotensin-converting enzyme returned to normal and was associated with symptomatic and objective clinical improvement We suggest that the serum activity of angiotensin-converting enzyme is helpful in diagnosing and assessing the activity of sarcoidosis and that serial determinations may be helpful in monitoring the dosage and duration of corticosteroid therapy.