Clinical evaluation of the captopril screening test for primary aldosteronism

In order to investigate the validity of angiotensin converting enzyme inhibition with captopril as a screening test for primary aldosteronism (PA), 50 mg of captopril were administered orally to 7 patients with PA, 17 with essential hypertension (EH), 5 with renovascular hypertension (RVH), 2 with renoparenchymal hypertension (RH) and 8 normal volunteers. The plasma aldosterone concentration (PAC) was suppressed to less than 15 ng/dl in all of the EH, RVH and RH patients and normal subjects 90 min after administration of captopril, but not suppressed in 6 of 7 patients with PA. In addition, the plasma renin activity (PRA) was increased to greater than 1 ng/ml/h in 10 of 17 patients with EH and in all with RVH, RH and the normal controls, but to less than that in 6 of 7 PA and the remaining EH patients. The PAC to PRA ratio after captopril was greater than 20 in all patients with PA, while it remained below 20 in EH, RVH and RH patients and normal controls. From these results, we conclude that the PAC to PRA ratio in the captopril administration test is a simple and useful tool to detect PA in hypertensive patients. In addition, the test has a great advantage in that it can be safely applied to outpatients with relatively severe hypertension.