Captopril test: time over?

The role of non-invasive tests for the detection of renovascular hypertension is still a matter of controversy. The 'captopril test' is widely used; its clinical usefulness, however, remains questionable. The aim of the current study was therefore to report our own experience and to review the published data on the diagnostic significance of the test.

Data from 485 hypertensive patients who underwent a captopril test in consecutive order at our institution were analysed retrospectively. After a 30-min resting period in the supine position 50 mg of captopril was given orally. Blood was collected before and 90 min after dosage for the determination of plasma renin concentration (normal range 3.5-8.0 ng/ml/h). An increase by 100% or more of the baseline value was considered a positive response. Blood pressure was recorded at baseline and at 90 min.

A positive response was present in 62 patients; further diagnostic work-up revealed significant renal artery stenosis in 11 of these patients. In the 423 patients with a negative response renal artery stenosis was found in three cases. With some limitations of retrospective analyses in mind, sensitivity and specificity of the test were calculated as 79% and 89%, respectively. No severe complication occurred during the test.

Our data on the diagnostic indices and the safety of the captopril test are in good agreement with most published series. Altogether, available data suggest that the captopril test has a limited diagnostic accuracy as a screening test for the detection of renovascular hypertension. New radiologic non-invasive techniques with greater diagnostic value are therefore likely to challenge the clinical role of the test in the future.