The Aldosterone-Renin Ratio and Primary Aldosteronism

Abstract

Before addressing performance characteristics of the ARR as a screening test, our study asked a more fundamental question: Is the assumption underlying its calculation valid?1Montori VM Schwartz GL Chapman AB Boerwinkle E Turner ST Validity of the aldosterone-renin ratio used to screen for primary aldosteronism.Mayo Clin Proc. 2001; 76: 877-882PubMed Scopus (85) Google Scholar Several of the points raised by Stowasser and Gordon serve to further discredit the ARR. Their comment that “no one experienced in this area would have expected to find a simple relationship” between PA concentration and PRA is the essence of the argument against the ARR. The concomitant effects of potassium and corticotropin also underscore the advocates’ disconnect in logic, since they do not propose dividing PA concentration by these other influential covariates. The admonition that the ARR should be measured twice exposes another weakness inherent to a calculation based on measurements that vary considerably within an individual. Of course, intraindividual variation also diminishes the effectiveness of alternative screening methods based on measurements of PA concentration and PRA. However, testimonials fall short of explaining how or why a single calculated number can provide more information than the 2 measured values required for calculation of the ARR. In 1949, Tanner2Tanner JM Fallacy of per-weight and per-surface area standards, and their relation to spurious correlation.J Appl Physiol. 1949; 2: 1-15PubMed Google Scholar summarized the troubled history of ratio variables in medicine: “Examples immediately came to light where investigators had drawn positive conclusions not justified by their data, … had proposed a less effective and more biased normal standard in preference to a more effective and less biased one, … and had invented a new clinical syndrome.” The findings of our study suggest that the ARR is no exception. The Aldosterone-Renin Ratio and Primary AldosteronismMayo Clinic ProceedingsVol. 77Issue 2PreviewTo the Editor: Montori and coworkers1 have attempted to discredit the aldosterone-renin ratio (ARR) as a screening test for primary aldosteronism (PAL) by reporting that, in a group of 497 patients with “previously diagnosed essential hypertension,” plasma aldosterone (PA) was only weakly dependent on plasma renin activity (PRA). The view is supported in an accompanying editorial by Kaplan.2 However, no one experienced in this area would have expected to find a simple relationship between PA and PRA, even in clinically normal individuals, because PA responds to potassium and corticotropin as well as to angiotensin II. Full-Text PDF