Test characteristics of the aldosterone-to-renin ratio as a screening test for primary aldosteronism

Background:The aldosterone-to-renin ratio (ARR) is a widely used screening test for primary aldosteronism. Current guidelines recommend a cut-off value of 91pmol/mU. Studies on its sensitivity, specificity, reproducibility and the role of medication have been conflicting. We prospectively assessed the test characteristics of the ARR and the effect of combination antihypertensive treatment.Methods:In 178 patients with persistent hypertension despite the use of at least two antihypertensives, plasma renin and aldosterone were assessed twice within an interval of 4 weeks. All patients underwent an intravenous salt loading test. A posttest plasma aldosterone exceeding 235pmol/l was considered diagnostic for primary aldosteronism. ARR was repeated after 4 weeks of standardized treatment with a calcium channel blocker and/or -adrenergic-receptor blocker.Results:The prevalence of primary aldosteronism was 15.2%. The median ARR was 35.0 (interquartile range 16.2-82.0) in primary aldosteronism versus 7.1 (2.2-17.5) pmol/mU in essential hypertensive patients (P<0.001). Under random medication, the ARR had 22.2% sensitivity and 98.7% specificity. On standardized treatment, the ARR rose from 9.6 (2.5-24.8) to 21.4 (10.8-52.1) (P<0.001). Multivariate regression showed that angiotensin-converting enzyme (ACE)-inhibitors and angiotensin II-receptor blockers were responsible for the lower ARR during random treatment. The area under the receiver operating characteristic curve was, however, similar under random and standardized treatment (84 vs. 86%, respectively, P=0.314). Bland-Altman plots showed an almost five-fold difference in ARR values taken under the same conditions.Conclusion:ARR sensitivity for primary aldosteronism is low when the recommended cut-off is used. Reproducibility is also poor, stressing the need for alternative screening tests.