captopril-renin stimulation test

Indications

• evaluation of hyperaldosteronism
• evaluation of refractory hypertension

Reference interval

• plasma aldosterone: < 15 ng/dL
• plasma renin: > 2 ng angiotensin I* /mL/hr

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)
  • primary hyperaldosteronism: > 50
  • essential hypertension: < 50

Procedure

• captopril 25 mg PO after an overnight fast
• patient should be seated during examination
• collect plasma (Na2EDTA) before & 2 hours after captopril for plasma aldosterone & plasma renin
• place in ice
• separate plasma & freeze promptly at -20 degrees C (stable for 1 year)

renin

* angiotensinogen ----------> angiotensin I

More general terms

• provocative clinical test

Additional terms

• captopril (Capoten)

Components

• aldosterone in serum/plasma
• renin in plasma