Evaluating Guideline-Endorsed Probability Stratification and Aldosterone Suppression Testing for Lateralizing Primary Aldosteronism

Background: Recent primary aldosteronism (PA) guidelines proposed probability-based stratifications, and use of aldosterone suppression testing, to predict lateralizing PA subtype. This guideline framework was based on very low-quality evidence. Methods: The discriminatory capacity of guideline-endorsed probability frameworks for PA subtyping were evaluated in this retrospective study of 319 PA patients, from two large tertiary centers in Bangkok, Thailand, who underwent subtyping assessments regardless of probability status. PA subtypes were determined by adrenal venous sampling (AVS) and/or post-adrenalectomy outcomes using PASO criteria. The main objectives were to evaluate the accuracy of predicting PA subtype using: 1) guideline-endorsed classification to high, intermediate, and low probabilities of lateralization; and 2) the seated saline suppression test (SST). Results: The majority of PA patients were characterized as having intermediate probability for lateralizing PA (75%); however, lateralizing PA was ultimately confirmed in 61-78% of all patients, regardless of guideline-based probability classification. The vast majority of SST results were positive using guideline-derived criteria, regardless of probability stratification or ultimate subtype: 89.3% of patients with lateralizing PA and 80.6% of those with bilateral PA had a positive SST. Among patients with intermediate probability of lateralizing PA, where guidelines specifically endorse the value of SST, the SST had a sensitivity of 89.4% and specificity of 22.0% for detecting lateralizing PA, with 78.0% false-positive and 10.6% false-negative rates. Consistently, post-SST aldosterone concentrations exhibited near-complete overlap between those with and without lateralizing PA. Conclusion: Guideline-endorsed probability frameworks, and the use of SST, lacked discriminatory capacity to predict PA subtype.