Captopril Test

Rationale: The administration of captopril, an angiotensin-converting enzyme inhibitor, produces an exaggerated rise in plasma renin activity (PRA) in patients with renovascular hypertension relative to patients with essential hypertension.^1,2 Postcaptopril PRA results meeting the following criteria suggest renovascular hypertension. All three criteria must be met.²

1. PRA >12 ng/mL/hour

2. Increase in PRA of at least 10 ng/mL/hour relative to baseline

3. Increase in PRA ≥150%, or of 400% if the baseline PRA is <3 ng/mL/hour

Protocol: The patient should be taken off antihypertensive medications and have normal salt intake for several days prior to test. The patient should remain seated throughout the test. An EDTA plasma sample should be drawn for renin activity (PRA). Administer 50 mg captopril orally. A second plasma sample for PRA should be drawn one hour after captopril dosing.¹

Orderable Test: Renin Activity, Plasma, Two Specimens (053686) (Baseline, one-hour)

Note: The captopril test has to been shown to produce false-positive results when used to screen patients with low risk of renovascular hypertension and high baseline PRA values.²

References

1. Muller FB, Sealey JE, Case DB, et al. The captopril test for identifying renovascular disease in hypertensive patients. Am J Med. 1986 Apr; 80(4):633-644. PubMed 3515933

2. Gerber LM, Mann SJ, Müller FB, et al. Response to the captopril test Is dependent on baseline renin profile. J Hypertens. 1994 Feb; 12(2):173-178. PubMed 8021469