Prevalence of unilateral hyperaldosteronism in primary aldosteronism: impact of a novel chemiluminescent immunoassay for measuring plasma aldosterone in Japan

This study aims to evaluate the prevalence of unilateral hyperaldosteronism (UHA) and its clinical characteristics in patients with primary aldosteronism (PA), diagnosed using plasma aldosterone concentration (PAC) measured by chemiluminescent enzyme immunoassay (CLEIA). We retrospectively analyzed data of 199 PA patients from the Japan Primary Aldosteronism Study II (JPAS II) dataset, including patients who underwent adrenal venous sampling (AVS) and the captopril challenge test (CCT) and/or saline infusion test (SIT), with PAC measured by CLEIA. We focused on two categories: confirmed PA, where patients exhibit clear biochemical evidence of the disorder, and borderline PA, where patients present with marginal biochemical indicators, as outlined in the Japan Endocrine Society's clinical practice guideline for the diagnosis and management of PA. In confirmed PA cases, over the half of patients was UHA, while approximately 15 to 20% of borderline cases were found to be UHA. The prevalence of hypokalemia was identified as predictor of UHA among borderline cases. Among borderline cases with no hypokalemia and adrenal nodules on CT imaging, only 6 to 8% of patients were found to have UHA. Notably, some patients exhibited UHA despite negative results on one test but confirmed result on the other, particularly those with hypokalemia or adrenal nodules on CT imaging. In conclusion, the findings validate the importance of AVS in confirmed PA cases and the need for careful assessment in borderline cases. When feasible, conducting both CCT and SIT, and interpreting their results alongside other clinical indicators, could provide a more comprehensive assessment.