Diagnosis of primary aldosteronism: Confirmatory test

The diagnosis of primary aldosteronism (PA) requires an Aldosterone-Renin-Ratio (ARR) to demonstrate a low or undetectable renin level and plasma aldosterone concentration that is inappropriately high for salt and volume status. The confirmatory tests are mandatory by the Endocrine Society Guideline for a definitive diagnosis of PA except if the patient presents spontaneous hypokalemia and Plasmatic Aldosterone Concentration (PAC) above 20 ng/dl plus Plasmatic Renin Activity (PRA) or Direct Renin Concentration (DRC) below assay detection limits. Then, the Endocrine Society Guideline recommends at least confirmatory test for confirmation or exclusion of the diagnosis of PA. Thanks to these confirmatory tests, the patients with negative confirmatory tests do not require unnecessarily invasive procedures such as adrenal vein sampling (AVS) or surgery. These tests are based on the premise that in PA the aldosterone secretion is at least partially autonomous from renin and therefore angiotensin release. Currently, there is no enough evidence to recommend one test over the others. The most employed suppression tests are saline infusion (intravenous infusion or orally), fludrocortisone (FST) or a captopril challenge (CCT) test. Several studies have compared the performance of these tests, but there is wide variability between them, the choice of confirmatory test and in threshold values between referral centers, because of differences in laboratory methodologies and patients' characteristics.