Captopril suppression versus salt loading in confirming primary aldosteronism

This prospective study was designed to compare the captopril suppression te st with the salt-loading approach to confirm the diagnosis of primary aldos teronism. A total of 49 patients were referred with a presumed diagnosis of primary aldosteronism. The captopril lest was performed in the morning wit h patients in the seated position after overnight fasting, Blood samples fo r plasma aldosterone were obtained before captopril administration (25 mg P O) and again 2 hours later. Patients were then subjected to a high salt die t (300 mmol sodium per day for 3 days). On the third day, urinary sodium (2 4 hours) was measured, and plasma aldosterone levels were measured at 8:00 AM (recumbent), and at noon (standing), Of the 49 patients, 44 had nonsuppr essible aldosterone concentrations with all the clinical characteristics of primary aldosteronism: 22 patients had surgically confirmed unique adenoma , and 22 patients had presumed bilateral hyperplasia. There was a significa nt correlation between plasma aldosterone values of salt-loaded patients (m ean of 8.00 AM and noon results) and the values 2 hours after captopril adm inistration (r=0.8. P <0.01). Plasma aldosterone cumulative distribution cu rves in primary aldosteronism patients (adenoma and hyperplasia) were not s ignificantly different between the 2 suppression tests. Our results showed that the captopril suppression test is as effective as sodium loading in co nfirming the diagnosis of primary aldosteronism.