From the Guidelines
To calculate the aldosterone to renin ratio, divide the plasma aldosterone concentration by the plasma renin activity, with a commonly used cutoff value of 30 when plasma aldosterone concentration is reported in nanograms per deciliter (ng/dL) and plasma renin activity in nanograms per milliliter per hour (ng/mL/h). This method is currently the most accurate and reliable means of screening for primary aldosteronism, as stated in the 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA guideline for the prevention, detection, evaluation, and management of high blood pressure in adults 1.
Important Considerations
- The plasma aldosterone concentration should be at least 10 ng/dL to interpret the test as positive 1.
- 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serum potassium in the normal range, and mineralocorticoid receptor antagonists (e.g., spironolactone or eplerenone) withdrawn for at least 4 weeks before testing 1.
- The diagnosis of primary aldosteronism generally requires a confirmatory test (intravenous saline suppression test or oral salt-loading test) 1.
Key Points to Keep in Mind
- The aldosterone:renin activity ratio can be influenced by the presence of very low renin levels 1.
- Certain medications, such as spironolactone and eplerenone, should be discontinued before testing to ensure accurate results 1.
- The patient's potassium levels should be normalized before testing to avoid false positives or negatives 1.
From the Research
Method for Calculating the Aldosterone to Renin Ratio
The aldosterone to renin ratio (ARR) is calculated by dividing the plasma aldosterone concentration by the plasma renin activity.
- The units of measurement for plasma aldosterone and renin can vary, making the calculation challenging 2, 3.
- A ratio of plasma aldosterone concentration (ng/dl) to plasma renin activity (ng/ml per hour) >20 is considered a positive screen for primary aldosteronism 4.
- The calculation of the ARR can be facilitated by the use of an application (App) that can perform the calculation regardless of the units of measurement used for plasma aldosterone and renin values 2, 3.
- The ARR is a key step in the early detection of primary aldosteronism, but it is not diagnostic on its own and must be confirmed by further testing 5, 4, 6.
- The ARR is calculated as follows: ARR = Plasma Aldosterone Concentration / Plasma Renin Activity.
- For example, if the plasma aldosterone concentration is 15 ng/dl and the plasma renin activity is 0.5 ng/ml per hour, the ARR would be 30 4.