A cross-sectional study of the effects of β-blocker therapy on the interpretation of the aldosterone/renin ratio: Can dosing regimen predict effect?

Context and aim: Aldosterone/renin ratio (ARR) is used as the primary screening tool for primary aldosteronism. Its interpretation is often challenging because of the interference of antihypertensive medication. β-blocker therapy suppresses renin production by inhibiting β-adrenergic receptors in the juxtaglomerular apparatus of the kidney and consequently aldosterone secretion (to a lesser extent). Therefore, β-blocker therapy has the potential to elevate the ARR. The aim of this study was to investigate whether or not the effect of β-blocker therapy on the ARR could be predicted from the dosing regimen. Methods: A prospective cross-sectional study was conducted. Participants were stratified into one of four groups (control/low/medium/high) based on the quantity of β-blocker prescribed. ARR was calculated from renin/aldosterone, measured using two assay systems. Results: Eighty-nine volunteers were recruited to our study. In the control group, zero patients had a positive ARR using plasma renin activity (PRA)/direct renin concentration (DRC). In the low, medium, and high-dose β-blocker groups between 8-25% of patients demonstrated screen positive ARR results for primary aldosteronism using DRC and PRA. DRC was significantly lower in patients in the medium/high-dose groups and PRA significantly lower in the low/medium/high-dose groups compared with controls. ARR using DRC was significantly higher in the medium/high-dose groups and ARR using PRA was significantly higher in the low/medium/high-dose groups compared with controls. Conclusion: Our study suggests that β-blocker therapy is associated with an increased risk of positive ARR screens for primary aldosteronism irrespective of the dose of β-blocker prescribed, in patients in whom it is clinically reasonable to expect that primary aldosteronism may be present.