Adrenal Venous Sampling Using Metanephrine in Primary Aldosteronism With or Without Cortisol Co-Secretion

Abstract Context The role of plasma metanephrine in adrenal venous sampling (AVS) for assessing lateralization in primary aldosteronism (PA) requires further clarification. Objective To evaluate the performance of plasma metanephrine in AVS for determining aldosterone lateralization in PA, with or without mild autonomous cortisol secretion (MACS). Methods Sequential AVS under cosyntropin stimulation was conducted in 58 consecutive patients with PA and indication for AVS. The selectivity index (SI) was assessed using plasma metanephrine (SIMN) and cortisol (SIC). The lateralization index (LI) for aldosterone was calculated using metanephrine (LIA/MN) and cortisol (LIA/C). Results Right SIMN was significantly higher than left SIMN (127.91 nmol/L [78.12, 239.12] vs. 46.16 nmol/L [26, 73.87]; p< 0.001). SIMN and SIC were strongly correlated in both the right adrenal vein (r=0.518, p< 0.001) and the left adrenal vein (r=0.435, p< 0.001). A SIMN > 6.45 demonstrated a sensitivity and specificity of 100%, outperforming the cut-off of 12 for identifying successful catheterization. Six cases with SIMN > 12 and SIC between 3 and 5 indicated that a SIC > 3 is sufficient for confirming successful cannulation. LIA/MN and LIA/C were significantly correlated (r=0.752, p< 0.001), with PA lateralization concordant in 93.1% of cases. Two discordant cases (unilateral PA by cortisol, bilateral by metanephrine) exhibited non-classical histology, which is associated with a higher risk of PA recurrence. MACS was identified in 15 out of 58 patients (25.86%) and generally did not influence AVS lateralization, except when aldosterone and cortisol were secreted by different adrenal lesions. Conclusion Metanephrine was superior to cortisol after cosyntropin for assessing selectivity and equivalent to cortisol for lateralization. Moreover, MACS did not impact lateralization in AVS under cosyntropin in most cases.