Reference Values for Aldosterone–Renin Ratios in Normotensive Individuals and Effect of Changes in Dietary Sodium Consumption

Abstract

BACKGROUND Determination of the aldosterone-to-renin ratio (ARR) in blood is the preferred screening test for primary aldosteronism. Renin can be measured as the plasma renin activity (PRA) or the plasma renin concentration (PRC). Consequently, the ARR can be measured either based on the PRA (ARRpra) or based on the PRC (ARRprc). In contrast with the ARRpra, the data on reference values for the ARRprc are limited. Moreover, whether the ARRpra or ARRprc is affected by variations in salt intake is unknown. METHODS We measured the PRA, the PRC, and serum aldosterone in 100 normotensive individuals between 20 and 70 years of age before and after a 3-day oral sodium-loading test (SLT). Participants were stratified according to age and sex. Data are presented as the median and interquartile range (IQR). RESULTS Urinary sodium excretion after the SLT was ≥200 mmol/24 h in all participants. Serum aldosterone, PRA, and PRC values were significantly reduced after the SLT. PRC and PRA results were highly correlated [Spearman rank correlation rs = 0.80 and 0.74 before and after SLT, respectively; P < 0.001 for both]. The central 95% reference intervals for ARRpra before and after SLT were 0.07–1.45 h−1 and 0.06–1.84 h−1, respectively. The corresponding reference intervals for ARRprc were 4.1–81.3 pmol/ng and 3.9–74.8 pmol/ng. The median ARRprc decreased after the SLT from 19.5 pmol/ng (IQR, 13.0–29.4 pmol/ng) to 18.6 pmol/ng (IQR, 9.4–27.1 pmol/ng) (P = 0.005), whereas the median ARRpra did not change (P = 0.12). Both the ARRprc and ARRpra at baseline were higher in women than in men, whereas no sex difference was observed after sodium loading. CONCLUSIONS We present reference values for the ARRprc for healthy individuals. The ARR is affected to a variable degree by sex and sodium intake.