SUN-247 - Real-World Evaluation of Saline Suppression Testing in Probability-Based Stratification of Primary Aldosteronism Management

Background
The updated 2025 Endocrine Society guideline for primary aldosteronism (PA) suggests using the results of the aldosterone suppression test (AST) in patients with an intermediate probability of lateralizing PA to guide subtyping and treatment decisions. However, clinical evidence supporting this probability-based strategy remains limited.

Methods
We conducted a retrospective single-center study at a tertiary referral hospital in Bangkok, Thailand. A total of 168 participants with a positive PA screen who underwent seated saline suppression testing (SST) between December 2020 and May 2024 were included. Patients were categorized as low, intermediate, or high probability of lateralizing disease based on the updated 2025 Endocrine Society guidelines (low = absence of hypokalemia with PAC < 11 ng/dL measured by immunoassay; high = resistant hypertension or hypokalemia with PRA < 0.2 ng/mL/h and PAC >20 ng/dL; intermediate = neither high nor low probability). The primary objective was to evaluate the performance of the SST in predicting subtype and treatment outcomes in patients labeled with an intermediate probability of lateralizing PA.

Results
The mean age of the population was 53 years, and 63% were female. At presentation, 80% had hypokalemia, and 4% had resistant hypertension. Overall, 9/168 patients were classified as low, 131/168 as intermediate, and 28/168 as high probability for lateralizing PA. Ultimately, 45/168 (27%) patients were confirmed to have lateralizing PA following AVS and/or unilateral adrenalectomy. In the intermediate probability group, 27/131 (21%) patients were found to have lateralizing PA, of which 5/27 (19%) had a negative SST result. Conversely, among the remaining 104 patients in the intermediate probability group who had non-lateralizing disease, 35/104 (34%) had a positive SST. Test characteristics of SST for detecting lateralizing PA in patients labeled intermediate probability were: sensitivity 81.5%, specificity 66.3%, positive predictive value 38.6%, and negative predictive value 93.2%. In the high-probability group, 11/28 (39%) patients were found to have non-lateralizing PA, of which 5/11 (45%) had positive SST results.

Conclusions
Prediction of lateralizing PA using AST after probability-based risk stratification provided excellent negative predictive value but only modest specificity, with a substantial risk for erroneously excluding those with lateralizing disease. These findings suggest that while SST may help triage patients, reliance on this approach alone may miss opportunities for cure, and selected patients still require AVS for definitive subtype evaluation.

Keywords: Primary aldosteronism, lateralizing, saline suppression test, probability

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