Abstract 53: Measurement of Peripheral Blood 18-Oxocortisol as the Diagnostic Method of Primary Aldosteronism and Its Subtypes

Abstract

Backgrounds: Primary aldosteronism (PA) is diagnosed and treated by the long steps, such as screening, confirmation testing and subtype diagnosis (computed tomography (CT) scan and adrenal venous sampling (AVS)). AVS has been the only reliable subtype classification method between surgically curable unilateral aldosterone producing adenoma (APA) and bilateral idiopathic hyperaldosteronism (BHA). In spite of increased numbers of specialized centers with superior ability of AVS in the world, unfortunately, this test is costly and requires a dedicated and expert radiologist; therefore it is not generally utilizable in most hospitals. It is understandable that easier diagnostic tools to be substitutes for AVS might be hoped by clinicians. Objective: The aim of the study was to determine the role of peripheral plasma levels of 18-oxo-cortisol (p18oxoF) and 18-hydroxycortisol (p18OHF) in differentiate APA from BHA. Patients: The study included 265 PA patients (113 patients with CT-positive macro APA, 31 patients with CT-negative micro APA and 121 patients with BHA) and 79 patients with essential hypertension (EH). Methods: All of 265 PA patients underwent AVS successfully, and any case with APA was surgically proven and pathologically confirmed including immunohistochemical analysis of steroidogenic enzymes. We measured p18oxoF and p18OHF of all PA patients by high sensitive LC ms/ms. Results: APA patients showed significantly higher p18oxoF and p18OHF than those of BHA patients and EH patients. The ROC analysis of p18oxoF in macro APA versus BHA demonstrated clinically useful discrimination with higher sensitivity of 0.83 and higher specificity of 0.99 by cutoff value of 4.7 (ng/dl), compared to the classification by p18OHF. Practically, 86 (76%) of macro APA patients with p18oxoF above 6.1 (ng/dl), which was the maximum level in BHA patients, might have been able to undergo surgery without AVS. Because the maximum p18oxoF in EH patients was 5.6 (ng/dl), the patients with p18oxoF above 6.1 (ng/dl) after screening of PA could also undergo surgery if unilateral adenoma(s) can be found on CT; thus it means omitting confirmation tests. Conclusions: Peripheral blood 18oxoF measurement can be a clinically useful method for the diagnosis of PA and its subtypes.