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.