Objective: To compare and contrast the diagnostic accuracy rates of two newer noninvasive screening tests for renovascular hypertension, the most common curable cause of secondary hypertension.
Patients and methods: One hundred fifty patients, thought to have a high probability of renovascular hypertension by established clinical criteria, underwent both the captopril challenge test and the renal scintigram with angiotensin-converting enzyme inhibitor, while on their usual antihypertensive regimen except angiotensin-converting enzyme inhibitors. If the result of either test was abnormal, angiography was undertaken, followed immediately by angioplasty (if a stenosis was found) or by renal vein renin determinations. Patients whose blood pressures were lower 6 to 12 weeks after a revascularization procedure (surgery or angioplasty) were diagnosed as having renovascular hypertension.
Results: Of the 150 patients, 100 underwent angiography, and 59 had renal artery stenosis. Of 53 patients who had surgery (n = 21) or angioplasty (n = 32), 51 had lowered blood pressures compared with before the procedure. Sensitivity and specificity of the tests were as follows: renal scintigram with angiotensin-converting enzyme inhibitor: 92% and 91% (all patients) and 92% and 80% (only patients with angiograms); captopril challenge test: 76% and 82% (all patients) and 76% and 58% (only patients with angiograms). Little difference in accuracy rates was observed in subgroup analyses in patients with chronic renal impairment, previous diuretic or beta-blocker therapy, or bilateral renal artery stenosis.
Conclusions: In selected, treated patients with a high probability of renovascular hypertension, the renal scintigram with angiotensin-converting enzyme inhibitor was a more accurate noninvasive screening test than the captopril challenge test. Noninvasive screening tests for renovascular hypertension can help to identify patients who should undergo angiography and often predict success after revascularization.