Measurement of plasma renin concentration instead of plasma renin activity decreases the positive aldosterone-to-renin ratio tests in treated patients with essential hypertension

CONDENSED ABSTRACT Aldosterone to renin ratio (ARR) was calculated in supine and standing position in 88 patients with essential hypertension while on their usual antihypertensive treatment measuring renin as plasma renin activity (PRA) and as plasma renin concentration (PRC) using a direct assay. For comparison ARR was evaluated also in ten patients with aldosterone producing adenoma (APA). We found that values of ARR calculated with the two methods (ARRP and ARRD) were highly significantly correlated and similar irrespective of body posture. Moreover assuming as thresholds of normalcy those recommended by the Endocrine Society Guidelines, i.e. 30 for ARRP and 3.7 for ARRD, we found 13 and 18 false positive ARRP respectively in the supine and standing position whereas, in the corresponding positions, there were 0 and 4 false positives with ARRD. Among patients with APA we found only one false negative ARRD. Thus the specificity of ARRD is greater than that of ARRP and excellent, particularly in the recumbent position, in spite of on going antihypertensive treatment.