Diagnostic value of captopril test in hypertensive patients with renal artery stenosis

To examine the utility of the single-dose captopril test in detecting renovascular hypertension (RVHT), the authors measured peripheral plasma renin activity (PRA), before and thirty and sixty minutes after an oral dose of captopril (25 mg), in 28 patients with RVHT and 22 patients with high-renin essential hypertension (EHT) without renal artery stenosis who were consuming 8 grams of sodium chloride per day. There was considerable overlap of individual values in basal PRA between the two groups. Sixty minutes after captopril, PRA was higher in RVHT than in EHT patients (74.8 +/- 63.9 versus 15.1 +/- 11.9 ng/mL/hr, P < 0.01). With the cutoff point set at 16 ng/mL/hr, RVHT was detected with a sensitivity of 96% and a specificity of 77%. The discriminating power was also superior to that based on blood pressure response to angiotensin II analogue under sodium depletion, rapid-sequence intravenous pyelography, or renography. These results show that captopril-stimulated peripheral PRA is an adequate screening tool for detecting RVHT in a population with high-renin hypertension.