Adrenal vein sampling (AVS) is the gold standard test for the subtyping of primary aldosteronism (PA). This procedure is hampered by unsuccessful bilateral cannulation of adrenal veins in up to two thirds of the cases depending on the cutoff of the selectivity index used. The rapid intra-procedural cortisol assay (IRCA) can increase the rate of bilateral success of AVS. This hypothesis needs to be proven using a randomized prospective study approach. We will therefore evaluate if an IRCA guiding adrenal vein sampling can increase the rate of selectivity and success of adrenal vein catheterization. With a total of 200 patients submitted to AVS, e.g. 100 patients in each arm, the study has 82% power to detect a 18% difference between arms at a two-sided α level =0.05. Given this power the study should allow to conclusively determine if IRCA is useful or not for improving the success rate of AVS. From the clinical standpoint this will be a major accomplishment in the field of the subtyping of PA considering the current disastrous situation regarding the clinical use of AVS.
