Aldosterone / Plasma Renin Direct Ratio (ARR), Plasma

What it is:
The Aldosterone / Plasma Renin Direct Ratio (ARR) test measures the relative levels of aldosterone (a hormone that regulates sodium, potassium, and blood pressure) and renin (an enzyme that controls aldosterone production). The ratio helps identify disorders of the adrenal glands and blood pressure regulation.

Uses

• Screen for primary hyperaldosteronism (Conn’s syndrome) in patients with high blood pressure and low potassium

• Differentiate between primary and secondary causes of hypertension

• Evaluate adrenal gland function

• Assist in diagnosing conditions such as adrenal adenoma or bilateral adrenal hyperplasia

Symptoms That May Lead to the Test

• Resistant or severe hypertension (high blood pressure not controlled by standard medications)

• Low potassium levels (hypokalemia)

• Muscle weakness or cramps

• Excessive thirst and frequent urination

• Family history of early-onset hypertension or stroke

Abnormal Results

• High ARR (elevated aldosterone with suppressed renin):

  • Suggests primary hyperaldosteronism (Conn’s syndrome) → usually from adrenal adenoma or hyperplasia

• Low ARR (both low or proportionally increased renin):

  • May suggest secondary hyperaldosteronism (due to kidney disease, heart failure, or diuretic use)

  • Can also indicate normal regulation depending on clinical context

Risks

• Minimal, limited to risks of a blood draw (mild pain, bruising, dizziness)

• Certain medications (e.g., diuretics, beta-blockers, ACE inhibitors, ARBs, steroids) can affect results — doctors often recommend stopping or adjusting these before testing