1. What is the Plasma Renin Aldosterone Ratio (ARR)?

The Plasma Renin Aldosterone Ratio (ARR) is a screening test used to identify primary aldosteronism, a condition characterized by excessive aldosterone production. It's calculated by dividing the plasma aldosterone concentration by the plasma renin activity.

2. How Does the Calculator Work?

The calculator uses the ARR formula:

Where:

• Aldosterone — Plasma aldosterone concentration in pg/mL
• Renin — Plasma renin activity in ng/mL/h

Explanation: The ratio helps identify cases where aldosterone production is inappropriately high relative to renin levels, suggesting autonomous aldosterone production.

3. Importance of ARR Calculation

Details: ARR is the primary screening test for primary aldosteronism, which is a common and potentially curable cause of hypertension. Early detection is important as it can lead to targeted treatment.

4. Using the Calculator

Tips: Enter aldosterone in pg/mL and renin in ng/mL/h. Both values must be greater than zero. For accurate results, patients should be off interfering medications when possible and samples should be collected in the morning after the patient has been upright for at least 2 hours.

5. Frequently Asked Questions (FAQ)

Q1: What is a normal ARR value?
A: Normal values vary by laboratory, but typically an ARR below 20-30 (pg/mL)/(ng/mL/h) is considered normal. Values above this threshold may suggest primary aldosteronism.

Q2: What medications can affect ARR?
A: Beta-blockers, ACE inhibitors, ARBs, diuretics, and NSAIDs can all affect renin and aldosterone levels. Patients should ideally be off these medications for 2-4 weeks before testing when possible.

Q3: When should ARR testing be considered?
A: Testing is recommended for patients with resistant hypertension, hypertension with hypokalemia, early-onset hypertension, or adrenal incidentaloma with hypertension.

Q4: What are the limitations of ARR testing?
A: ARR can be affected by many factors including medications, sodium intake, time of day, and posture during blood sampling. Confirmatory testing is usually required for diagnosis.

Q5: What follow-up tests are needed if ARR is elevated?
A: Confirmatory tests may include saline infusion test, captopril challenge test, or oral sodium loading test, followed by adrenal CT scanning and adrenal venous sampling.