The saline infusion test (SIT) is a common confirmatory test for primary aldosteronism (PA). According to the guideline, a post‐infusion plasma aldosterone concentration (PAC) of 5‐10 ng/dl is considered indeterminate, and recommendations for diagnostic strategies are currently limited in this situation. The objective of the study was to explore whether an addition of the captopril challenge test (CCT) could improve the diagnostic accuracy in patients with indeterminate SIT. A total of 280 hypertensive patients with high risk of PA completed this study. Subjects were defined as SIT indeterminate based on their PAC post‐SIT. These patients then underwent the CCT where PACs post‐CCT >11 ng/dL were considered positive. Using fludrocortisone suppression test (FST) as the reference standard, diagnostic parameters including area under the receiver‐operator characteristic curves (AUC), sensitivity and specificity were calculated. For patients under investigation for possible PA who have indeterminate SIT results, an addition of CCT improves the diagnostic accuracy.
