Enzyme immunoassay for plasma renin activity: II. Clinical application.

The application of an enzyme immunoassay for plasma renin activity in clinical diagnosis was studied and the following findings were obtained: 1. In patients with primary aldosteronism, very low renin activities were found. On the other hand, increased renin levels were observed in patients with secondary aldosteronism (renal artery stenosis, malignant hypertension, Bartter's syndrome). 2. Plasma renin activity was found to be considerably increased in Addison's disease. Measurements of Plasma renin were a guide-line for appropriate mineralocorticoid substitution in those patients. In 6 patients with salt-losing congenital adrenal hyperplasia due to 21-hydroxylase deficiency, the renin activity was also elevated and normalized after corticoid treatment. 3. During pregnancy, the renin levels showed an increasing tendency from the first to third trimester. Women with pre-eclampsia showed higher values than normal pregnant women. 4. An age-dependent change of renin activity was observed in newborns and children, especially markedly increased values during the first 5 days of life. 5. During the normal menstrual cycle the renin levels increased to a maximum in the mid-luteal phase. A significant increase of renin activity was found in women taking oral contraceptives. Previously, we reported on the determination of renin activity by an enzyme immunoassay (EIA) (Hubl et al., 1980). In this study, we examined the clinical application of this EIA.