Comparing ARR Versus Suppressed PRA as Screening Tests for Primary Aldosteronism

BACKGROUND: In many practices, the screening for primary aldosteronism relies on a single-blood draw for plasma aldosterone concentration (PAC) and plasma renin activity (PRA) to establish an aldosterone-to-renin ratio (ARR). ARR levels vary between expert centers and repeated assays in the same individual, emphasizing the potential variability of this screening approach. A suppressed PRA to <1 ng/mL per h has been proposed as an alternative test to the ARR. METHODS: We compared 2 potential screening approaches to identify probable primary aldosteronism (ARR >= 30 or ARR >= 20 versus PRA suppressed below 1 ng/mL per h) in a cohort of 94 829 paired PRA and PAC samples submitted by clinicians to evaluate the presence of primary aldosteronism. RESULTS: Of 94 829 patients, 20.3% tested positive based on ARR >= 20 (95% CI, 20.0%-20.5%), 13.9% based on ARR >= 30 (95% CI, 13.6%-14.1%), versus 45.9% based on suppressed PRA (<1 ng/mL per minute [95% CI, 45.5%-46.2%]). In the PRA group, a range of aldosterone levels was observed: 5.5% had PAC >15 ng/dL, 25.2% had PAC 5 to 15 ng/dL, and 15.2% had PAC <5 ng/dL, compared with 6%, 12.7%, and 1.6% in the ARR >= 20 group and 4.7%, 8.5%, and 0.7% in the ARR >= 30 group. CONCLUSIONS: In this cohort of individuals being screened for primary aldosteronism, substantially more individuals were identified using criteria focused on suppression of renin activity compared with using the aldosterone renin ratio as a screening tool.