The diagnostic value of the 24 hour integrated concentration of plasma aldosterone

The 24-hour urinary excretion rate of aldosterone, the 24-hour integrated concentration of plasma aldosterone (IC-ALDO) and the morning plasma aldosterone levels from a single, discrete venipuncture of 92 subjects (30 normal subjects, 62 patients with mild, essential hypertension) were compared, using the variance ratio method, to 12 patients with primary aldosteronism. The variance of the IC-ALDO was significantly lower than the respective variances of the 24-hour urinary excretion of aldosterone (P less than 0.01) and of the discrete, morning plasma levels of aldosterone (P less than 0.01). The clinical usefulness of this diagnostic procedure depends on its ability to discriminate between healthy subjects and various hypertensive patients. Because of its narrower variance and enhanced discriminatory ability, the 24-hour IC-ALDO may have useful application in diagnosis of various disorders of aldosterone secretion. We have found the IC-ALDO completely separated 11 of 12 primary aldosteronism patients (mean 36 +/- 17) from essential hypertensive controls (mean 9.6 +/- 4.1) (P less than 0.01). When IC-ALDO was combined with integrated concentration of plasma renin activity in an ALDO/RENIN ratio, all 12 primary aldosteronism patients were diagnosed.