PP.27.04] COMPARISON BETWEEN CORTISOL, FREE METANEPHRINE AND THE FREE/TOTAL METANEPHRINE RATIO TO ASSESS SELECTIVITY OF ADRENAL VEIN SAMPLING

Abstract

Objective: Primary aldosteronism (PA) is one of the most common forms of secondary hypertension, which can be cured by surgical removal of an adrenal gland if aldosterone secretion is lateralized. Adrenal vein sampling (AVS) is the gold standard method to assess lateralization of aldosterone secretion in PA. Recently, the use of free metanephrine (fMN) instead of cortisol has been proposed to determine correct positioning of the catheter during AVS (selectivity). As almost all fMN is released by the adrenal glands to be sulphate-conjugated peripherally. We hypothesized that free/total metanephrine ratio (FTMR) measured in each adrenal vein would be non inferior to fMN to assess selectivity. The objective of the study was to compare the FTMR to fMN and cortisol to assess selectivity. Design and method: cortisol, free and total metanephrines were measured in the distal and proximal veina cava and in the right and left adrenal veins in patients with PA referred for sequential, non cosyntropin-stimulated AVS. Correct placement of the tip the catheter was assessed by computed tomography angiography (CTA). Receiver operating characteristic (ROC) curves were used to assess the performance of each marker independently of cut-off choices. Results: 76 patients (37 women) were included in the study. Mean age (±SD) was 51.3 ± 9.7 years. Of those, 56 had a successful positioning of the tip of the catheter ascertained in both adrenal veins. ROC curve analyses on the left adrenal vein established an area under the curve (AUC) of 1.0 ± 0 for both free metanephrine and the FTMR compared to an AUC 0.966 ± 0.015 for cortisol. In the right adrenal vein, AUC were respectively 0.967 ± 0.020, 0.968 ± 0.20, and 0.824 ± 0.044 for FTMR, free metanephrine and cortisol. Cut-offs values for the selectivity index determined by ROC for FTMR, fMT and cortisol were respectively 0.41, 10.0 and 2.63 on the left and 0.30, 9.9 and 2.5 on the right. Conclusions: The use of the FTMR performs similarly to fMN to assess the selectivity of the adrenal vein catheterization. Its use could limit the number of blood samples and time of the procedure as only blood from the adrenal veins is necessary.