Aldosterone, Renin and ARR Variability in Screening for Primary Aldosteronism

The plasma aldosterone concentration (PAC), renin and aldosterone-renin ratio (ARR) are used to screen for primary aldosteronism (PA). Substantial intra-individual variability of PAC and ARR using plasma renin activity in the context of usual antihypertensive therapy has been described, but there is no data on ARR variability calculated using direct renin concentration (DRC). The objective of the study was to describe the intra-individual variability of PAC, DRC and ARR in the absence of interfering medications, in patients with and without PA. Analysis of 223 patients (55% female, median age 52 years), including 162 with confirmed PA, demonstrated high variability with a sample CV of 22-25% in the PAC and sample CV of 41-42% in the DRC and ARR, in both the PA and non-PA groups. The degree of variability was substantially higher than the assays’ analytical CV. Sixty-two patients (38%) with PA had at least one ARR below 70 pmol/L:mU/L (2.4 ng/dL:mU/L), a cut-off for first line screening of PA. Significant intra-individual variability in PAC, DRC and hence ARR occurs in a large proportion of patients being investigated for PA. These findings support the need for at least two ARR before PA is excluded or further investigated.