P-534: Predictive value of the aldosterone-renin ratio in screening for primary aldosteronism

Abstract

Although the aldosterone-renin ratio (ARR) is frequently used to distinguish whether further testing for primary aldosteronism (PA) is indicated, its predictive value (PV) has not been determined in population based samples representative of patients with essential hypertension (EH). To do so, we considered 280 adults recruited through a diagnostic index of all residents of Olmsted County, MN with a previous diagnosis of EH. Of these, 140 individuals with stage I-II EH agreed to participate and 117 subjects (72 men, 45 women [age 52±7 years]) successfully completed both an aldosterone suppression and a renin stimulation test to confirm the diagnosis of PA. In this sample, the prevalence of PA was 12±6% based on 24 hour urinary aldosterone ≥12 μg with urinary sodium ≥200 mEq, plasma renin activity (PRA) ≤1.0 ng/mL/hr on high sodium intake, and PRA ≤3.4 ng/mL/hr after oral furosemide diuresis (2 mg/kg body weight x 2). Values of the ARR ≥20 were considered “positive.” The test characteristics of the ARR were: sensitivity 69%, specificity 82%, postive PV 38% and negative PV 94%. These results suggest that, among patients with previously diagnosed EH, most with an elevated ARR (62%) do not have PA and some with a normal ARR may still have PA (6%). At these levels of sensitivity and specificity, the negative PV of a normal ARR to exclude the diagnosis of PA will diminish progressively as individuals at higher risk of PA are screened. Thus, given the test characteristics of the ARR, confirmatory testing is still required to establish the diagnosis of PA in low risk patients with an elevated ARR or to exclude the diagnosis in high risk patients with a normal ARR.

Renin, Aldosterone, Screening Test

© American Journal of Hypertension, Ltd. 2002