The not-so-shortcomings of seated saline suppression testing in primary aldosteronism

Tsai and colleagues1 recently reported poor performance of aldosterone suppression testing (AST) in detecting patients who may have lateralizing primary aldosteronism (PA), rendering them candidates for adrenal venous sampling (AVS). From a cohort of 2482 with high probability features of PA, they selected 531 who had both seated saline suppression testing (SSST) and a captopril challenge test (CCT). Their interpretation of the data led them to conclude that AST adds little to the diagnostic evaluation of PA and may lead to missed opportunities for targeted surgical treatment and potential cure. We disagree with this conclusion based on concerns regarding the study's design, methodology, data quality and interpretation. Using the more sensitive aldosterone cut-off of >6 ng/dL (2), the SSST actually performed very well. Over 97% of the 531 patients with high probability PA were positive, consistent with high test sensitivity. Of the 153 with clinically overt PA, the sensitivity was 98%. The sensitivity for lateralizing PA was similarly excellent at 98% and was even better for patients cured biochemically (99%) or clinically (100%) by unilateral adrenalectomy according to PASO criteria.2 It's hard to think of any other dynamic test in endocrinology that would perform better.