The simplified captopril test: an effective tool to diagnose renovascular hypertension

There is much variability among reports of the accuracy of the captopril test for renovascular hypertension. Factors that contribute to this variability include a lack of consistency in diagnostic criteria, the preparation of the patient and the performance of the test, and the criterion standard (renal artery stenosis or renovascular hypertension). We investigated the sensitivity and specificity of a simplified version of the test, based on a single postcaptopril value of plasma renin activity, in 36 patients who were undergoing either angioplasty or surgery for renal artery stenosis. The test demonstrated an excellent sensitivity (96%) but a poor specificity (55%). However, the poor specificity was related to certain clinical characteristics; high baseline plasma renin activity measurements, female gender, current smoking, renal dysfunction, and bilateral renal artery stenosis were all associated with false-positive results. This simplified captopril test, when applied to a population with a high prevalence of renovascular hypertension and performed in a standardized manner, can accurately identify those patients unlikely to respond to intervention. However, a positive test, especially in those with the characteristics noted above, does not help clinical decision making because of the limited test specificity.