What is the normal plasma renin (Renin) to aldosterone (Aldosterone) ratio?

From the Guidelines

The normal plasma renin-aldosterone ratio (ARR) is typically less than 30 when aldosterone is measured in ng/dL and renin in ng/mL/hr. This ratio is an important screening tool for primary aldosteronism, with values above 30-40 suggesting this condition 1. Normal aldosterone levels generally range from 2-20 ng/dL in the upright position, while plasma renin activity typically ranges from 1-4 ng/mL/hr when upright. These values can vary based on posture, sodium intake, time of day, and laboratory methods.

Key Considerations

• When interpreting ARR results, it's essential to consider that certain medications can affect these values - antihypertensives like beta-blockers and ACE inhibitors can alter renin levels, while diuretics can affect both renin and aldosterone 1.
• For accurate assessment, these medications should ideally be discontinued for 2-4 weeks before testing, though this must be balanced with patient safety.
• The ratio works by identifying inappropriate aldosterone production relative to renin levels, which occurs in conditions like primary aldosteronism where aldosterone production becomes autonomous from the renin-angiotensin system.

Clinical Implications

• A high ratio (> 20) when the serum aldosterone is >16 ng/dL and PRA is <0.6 ng/mL per hour is suggestive of primary aldosteronism, particularly in a patient taking an ACE inhibitor or ARB 1.
• Further assessments are required to confirm the diagnosis, including a confirmatory test such as an intravenous saline suppression test or oral salt-loading test.

Testing Conditions

• Patients should have unrestricted salt intake, serum potassium in the normal range, and mineralocorticoid receptor antagonists (e.g., spironolactone or eplerenone) withdrawn for at least 4 weeks before testing 1.

From the Research

Normal Plasma Renin and Aldosterone Ratio

The normal plasma renin and aldosterone ratio can vary depending on several factors, including the method of measurement and the population being studied.

• The aldosterone-to-renin ratio (ARR) is used as a screening test for primary aldosteronism, with different studies suggesting different cut-off values for this ratio 2, 3.
• One study found that the best cut-off value for the plasma aldosterone/plasma renin activity ratio was 69, which corresponded to a sensitivity of 96% and a specificity of 85% for diagnosing primary aldosteronism 2.
• Another study found that the central 95% reference intervals for the ARR based on plasma renin activity (ARR(pra)) were 0.07-1.45 h(-1) and 0.06-1.84 h(-1) before and after a sodium-loading test, respectively 3.
• The same study found that the corresponding reference intervals for the ARR based on plasma renin concentration (ARR(prc)) were 4.1-81.3 pmol/ng and 3.9-74.8 pmol/ng before and after the sodium-loading test, respectively 3.
• The ARR can be affected by factors such as sex and sodium intake, with one study finding that the median ARR(prc) decreased after a sodium-loading test and was higher in women than in men at baseline 3.

Factors Affecting the Ratio

Several factors can affect the plasma renin and aldosterone ratio, including:

• Sodium intake: High sodium intake can suppress renin and aldosterone production, while low sodium intake can stimulate their production 3.
• Sex: Some studies have found that the ARR is higher in women than in men, although this difference may not be present after sodium loading 3.
• Age: The ARR may vary with age, although the exact relationship between age and the ARR is not well established 3.
• Method of measurement: The ARR can be measured using different methods, including plasma renin activity and plasma renin concentration, which may give different results 3.

Clinical Significance

The plasma renin and aldosterone ratio is an important diagnostic tool for primary aldosteronism, a common cause of secondary hypertension 4, 5, 6.

• A high ARR can indicate autonomous aldosterone production, which can lead to hypertension and other cardiovascular problems 4, 5, 6.
• The ARR can be used to screen for primary aldosteronism in patients with hypertension, particularly those with resistant hypertension or hypokalemia 5.
• Confirmatory testing, such as the captopril challenge or fludrocortisone suppression test, is necessary to diagnose primary aldosteronism in patients with a high ARR 5.