SHORT-TERM VARIABILITY OF THE ALDOSTERONE-TO-RENIN RATIO IN AN ESSENTIAL HYPERTENSIVE POPULATION

Abstract

Objective: The aldosterone-to-renin ratio (ARR) is a commonly used metric in the screening of primary aldosteronism. However, insufficient high-quality research evaluating its precision and accuracy is available. In particular, limited information is known with regard to intra-patient short-term variability in the ARR. Highly variable intra-patient values could severely hamper the ability of the ARR to effectively screen for primary aldosteronism. Design and method: 68 unmedicated, essential hypertensive participants (female n = 26, male n = 42), had two blood samples taken in the morning measuring plasma aldosterone and active plasma renin concentration within a 2-hour time window under strictly standardised conditions and while consuming a regulated sodium intake (3 g/day). Bland-Altman plots, mountain plots and correlation analysis were performed, comparing the mean values per participant with the difference between their measurements. Results: Using Bland-Altman plots, we found that renin, aldosterone and the ARR become increasingly variable as their mean values increase. Correlation analysis of the absolute difference in aldosterone-to-renin ratio values between measurements and their mean resulted in an R-squared value of 34.7% (p-value < 0.000)). This trend was also noted for plasma aldosterone (R-squared 9.6%; p-value 0.010) and active plasma renin concentration (R-squared 7.9%; p-value 0.021) separately. Taking an ARR value above 30 as abnormally high, 29.4% of the participants with a mean value above 30, had one measurement below 30. Conversely, 3.9% of those with mean values below 30 had one measurement above 30. Conclusions: Based on our findings, it can be concluded that spot measurements of the aldosterone-to-renin ratio have acceptable short-term variability in the lower ranges, but have increasingly doubtful reliability as aldosterone-to-renin values rise. Thus, in a clinical context, great caution should be taken in interpreting spot measurements of moderate to high aldosterone-to-renin ratio values, in particular when values are mildly elevated.