Plasma aldosterone by radioimmunoassay determination in normal man and in patients on maintenance haemodialysis.

The plasma aldosterone concentration was measured by a radioimmunoassay in which paper chromatography was used for separation of the steroids. The method had a low blank value (1.3 plus or minus 2.8 pg/ml), and the sensitivity was 6 pg/ml. The variation coefficients for interassay and intraassay determinations were 13.0% and 9.4%, respectively. An accuracy study on fixed amounts of unlabelled aldosterone added to pool-plasma gave a linear correlation (slope equals 0.9973). In a normal material, the mean plasma aldosterone concentration was found to be 120 pg/ml. In 26 patients on maintenance haemodialysis the mean plasma aldosterone concentration was 68 pg/ml, in the group of anephric patients 36 pg/ml, and in the non-nephrectomized group 91 pg/ml. There was a significant difference (P smaller than 0.01) between the two groups as well as between the total group of patients on maintenance haemodialysis and the normal subjects.