Comparison of a Biological and an Immunological Assay for the Measurement of Plasma Renin Activity

The present study was undertaken to compare the values of plasma renin activity measured by both a bioassay (Skinner method) and by a radioimmunoassay procedure (Haber method). In 28 normal subjects, mean immunoassayable plasma renin activity (PRA) of 1.2 ng/ml/hr ± 0.1 se was not significantly different from the mean normal value of 1.3 ng/ml/hr ± 0.1 se determined by bioassay. Similarly, of 26 patients with either essential or renovascular hypertension, peripheral venous PRA measured by immunoassay did not differ from that determined by bioassay (p > 0.30). The correlation coefficient of 0.97 obtained by comparing the values from the 2 methods was highly significant (p 0.30). Renin disappearance curves with both methods were similar in each of 2 patients following bilateral nephrectomy. In 2 groups of dogs, a significant correlation between both renin methods was demonstrated in response to hemorrhage and in response to furosemide induced diuresis (p < 0.01) ; the actual values measured by the 2 methods were not significantly different. Overall, these results demonstrate a close correspondence between the renin activities determined by the Haber radioimmunoassay and Skinner bioassay procedures. However, in a number of individual instances, the correspondence was relatively poor.