Aldosterone-to-Potassium Ratio for Predicting Lateralized Primary Aldosteronism in Patients with Unilateral Adrenal Nodules

Background: Adrenal vein sampling (AVS) is the standard method for subtyping primary aldosteronism (PA) and selecting candidates for adrenalectomy. However, its application is limited by restricted availability and the risk of catheterization failure, which requires experienced operators. Markedly elevated aldosterone levels, severe hypokalemia, and unilateral adrenal nodules are commonly observed in lateralized PA and may aid in subtyping. Objective: To evaluate the aldosterone-to-potassium ratio (APR) for predicting lateralized PA in patients with unilateral adrenal nodules. Materials and Methods: The present study was a retrospective study that included PA patients with unilateral adrenal nodules and successful AVS between January 2012 and December 2024. Lateralized and bilateral PA were classified based on AVS. The APR was compared between subtypes, and its utility for subtyping PA was assessed. Results: Of 85 patients, the median age was 56 years and 53% were men. Fifty-one patients (60%) had lateralized PA and 34 (40%) had bilateral PA. Serum potassium was lower in patients with lateralized PA compared to those with bilateral PA at 2.8 versus 3.2 mmol/L (p<0.01), and plasma aldosterone concentration was higher at 29 versus 18 ng/dL (p<0.01). The median APR was significantly higher in the lateralized group at 12.4 versus 6.2 ng/dL:mmol/L (p<0.01). An APR threshold of 12 predicted lateralized PA with an AUC of 0.796 (p<0.001), yielding 57% sensitivity and 91% specificity. Conclusion: The APR may serve as a practical tool for predicting lateralized PA in patients with unilateral adrenal nodules. Its diagnostic performance supports its role as a supplementary method for subtyping when AVS is not feasible.