Background: 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, which can occur 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 can be proven using a randomized prospective study design approach.Aim: We will therefore evaluate if an IRCA-guided AVS strategy can increase the rate of selectivity and thus the success rate of adrenal vein catheterization.Methods: Consecutive patients with a biochemical diagnosis of PA, seeking surgical cure, willbe randomized to undergo AVS according to an IRCA-sham or an IRCA-guided procedure.Experimental and endpoint will be the rate of bilaterally selective AVS studies as defined bya selective index cutoff > 2.00 value under baseline (unstimulated) conditions. With 100 patients submitted to AVS with a normal procedure and 100 patients undergoing AVS with IRCA,it has been estimated that the study has 82% power to detect a significant difference of 18%at a two-sided 0.05 significance level between arms.Expected results. Given this power we expect to the able to determine if IRCA is useful or not for improving the success rate of AVS. Given the current disastrous situation regarding the clinical use of AVS this will be a major accomplishment in the field of the subtyping ofPA.
