captopril-renin stimulation test

Indications: - evaluation of hyperaldosteronism - evaluation of refractory hypertension Normal range: 1) plasma aldosterone: < 15 ng/dL 2) plasma renin: > 2 ng angiotensin I* /mL/hr Procedure: 1) captopril 25 mg PO after an overnight fast 2) patient should be seated during examination 3) collect plasma (Na2EDTA) before & 2 hours after captopril for plasma aldosterone & plasma renin 4) place in ice 5) separate plasma & freeze promptly at -20 degrees C (stable for 1 year) renin * angiotensinogen ----------> angiotensin I Clinical significance: - in primary hyperaldosteronism, plasma aldosterone remains high & plasma renin remains low after captopril - occasional patients with essential hypertension may have elevated aldosterone with diminished renin activity - ratio of aldosterone to plasma renin activity (after captopril) a) primary hyperaldosteronism: > 50 b) essential hypertension: < 50

References

Clinical Guide to Laboratory Tests, 3rd ed. Teitz ed., W.B. Saunders, 1995

Components

aldosterone in serum/plasma renin in plasma