To the Editor.
—I read with interest the article by Hiramatsu et al entitled "A Screening Test to Identify Aldosterone-Producing Adenoma by Measuring Plasma Renin Activity: Results in Hypertensive Patients" in the November Archives (1981;141:1589-1593).These authors showed that in the upright position, the aldosterone-plasma renin activity (PRA) ratio was always above 400 in all their hypertensive patients with aldosterone-producing adenoma (APA) and was below 200 in patients with essential hypertension. A false-positive value was also found in some of their patients with essential hypertension. The administration of diuretics and salt restriction did not increase the aldosterone-PRA ratio in their patients with essential hypertension.Using amiloride hydrochloride as a potassium-sparing diuretic, which also has an antihypertensive effect,1-3 20 to 30 mg/day for longer than eight weeks, we have examined four hypertensive patients with APA and seven patients with essential hypertension. Blood samples were obtained from the patients at 9:30