The captopril test for identifying renovascular disease in hypertensive patients

To develop a screening test for identifying renovascular hypertension, the blood pressure and plasma renin activity responses to an oral test dose of captopril were studied in 246 quietly seated hypertensive patients. The following criteria were developed that exploit the hyperresponsiveness of renin secretion in renovascular hypertensive patients: a 60-minute post-captopril plasma renin activity of 12 ng/ml per hour or more and an absolute plasma renin activity increase of 10 ng/ml per hour or more, along with a 150 percent increase in plasma renin activity (or a 400 percent increase if the baseline plasma renin activity was below 3 ng/ml per hour). Retrospectively, the test identified, among 200 hypertensive patients without evidence of renal dysfunction, all 56 patients with proved renovascular disease. In this group, false-positive results occurred only in two of 112 patients with essential hypertension and in six with secondary hypertension. Nine untreated patients had blood pressure levels of less than 160/100 mm Hg. The test was neither as sensitive nor specific in the 46 patients with renal insufficiency. This study demonstrates that the renin response to oral captopril is a useful screening test for identifying patients with unilateral or bilateral renovascular disease. Since the test also characterizes the renin dependency of the hypertension, it may have other diagnostic and therapeutic uses.