SUN-LB98 RAAS Triple-A Analysis for the Screening of Primary Aldosteronism

Primary aldosteronism (PA) is recognized as the most frequent cause of secondary hypertension, and its screening is expected to become a routine evaluation in most patients with hypertension. The interference of antihypertensive therapies with the aldosterone-to-renin ratio (ARR) during screening process is a major confounder. Renin-Angiotensin-Aldosterone System Triple-A (RAAS Triple-A) testing is a novel mass-spectrometry based assay for quantification of Angiotensin I (Ang I), Angiotenisn II (Ang II) and Aldosterone in a single sample of serum by RAAS equilibrium analysis. Obtained hormone levels are used to calculate markers for plasma-renin-activity (PRA-S, Ang I + Ang II), plasma angiotensin-converting-enzyme activity (ACE-S, Ang II-to-Ang I ratio) and adrenal function (AA2-Ratio, Aldosterone-to-Ang II ratio), with the latter being useful to screen for PA in hypertension. We performed a comparative evaluation of the diagnostic performance of the AA2-Ratio and 5 renin-based diagnostic ratios, differing in methods to determine aldosterone levels and renin activity in a cohort of 110 patients with hypertension (33 patients with confirmed primary aldosteronism and 77 with essential hypertension). All ratios showed comparable areas under the curves ranging between 0.924 and 0.970 without significant differences between each other. The evaluation of the ACE-S revealed persistent drug intake in some patients as cause for suppressed renin-based diagnostic ratios, while the AA2-Ratio remained unaffected. The Youden index optimal cutoff value for the AA2-Ratio was 6.6 ([pmol/L]/[pmol/L]) with a sensitivity of 90% and a specificity of 93%, proving non-inferiority compared with the ARR while pointing to the potential for an interference-free application in patients under ACE inhibitor therapy. This study shows for the first time the accuracy and reliability of RAAS Triple-A analysis for the screening of primary aldosteronism that can be applied in clinical routine.