P052 OPTIMAL ADRENAL VEIN SAMPLING LATERALIZATION CRITERIA FOR DIAGNOSIS OF UNILATERAL PRIMARY ALDOSTERONISM USING ALDOSTERONE CONCENTRATION MEASURED BY LC-MS/MS POST-ACTH STIMULATION

Background: Primary aldosteronism (PA) is characterized by excessive, autonomous secretion of aldosterone from one or both adrenal glands. Identification of unilateral disease and surgical resection can lead to cure, and is dependent on accurate criteria for lateralization of excess aldosterone during adrenal vein (AV) sampling (AVS). Current evidence for AVS lateralization cut-offs using plasma aldosterone concentration (PAC) measured by LC-MS/MS and post-surgical outcomes is limited. Aim: To determine optimal cut-off criteria to define lateralization of PA on AVS based on PAC measured by LC-MS/MS post-ACTH stimulation and post-surgical outcomes data. Methods: This study involved 60 subjects with PA who had PAC measured by LC-MS/MS post ACTH-stimulation during bilaterally-cannulated AVS, underwent unilateral adrenalectomy between July 2015-July 2021 and were followed up for ≥6 months. AVS lateralization parameters (lateralization index [LI; dominant PAC/cortisol(AV) ÷ non-dominant PAC/cortisol(AV)], contralateral suppression index [CSI; non-dominant PAC/cortisol(AV) ÷ PAC/cortisol(Peripheral Vein)], lateralization ratio [LR; dominant PAC/cortisol(AV) ÷ PAC/cortisol(Peripheral Vein)] and post-surgical outcome data were examined. Complete biochemical remission (CR) of PA post-surgery was defined using PASO International Consensus Criteria. Receiver operating characteristic (ROC) analysis was performed to determine optimal cut-offs for LI, CSI and LR based on cases who achieved CR of PA post-surgery (n=55) vs those who did not (n=5). Results: Optimal cut-off LI during ACTH-stimulated AVS to identify unilateral PA cases who achieved CR post-surgery was 5.1 (AUC=0.92, P<0.001; 92.7% sensitivity, 80.0% specificity) while the optimal cut-off for CSI was 0.6 (AUC=0.887, P<0.001; 82.1% sensitivity, 100.0% specificity), and for LR was 3.3 (AUC=0.695, P=0.202; 80.0% sensitivity, 80.0% specificity). Cases with LR of 2.0-3.3 also achieved CR post-surgery if it was associated with CSI <0.6. Conclusion: LI of >5.1 provides high sensitivity and CSI <0.6 high specificity for identification of surgically curable unilateral PA during ACTH-stimulated AVS when PAC is analyzed by LC-MS/MS.