From the Guidelines
The initial lab test for primary hyperaldosteronism is the aldosterone-to-renin ratio (ARR). This screening test should be performed in the morning after the patient has been upright for at least 2 hours, and ideally after the patient has been on an unrestricted sodium diet. Blood samples are collected to measure both plasma aldosterone concentration and plasma renin activity (or direct renin concentration). An elevated ARR, typically greater than 20-40 (depending on the laboratory's reference range and units used), suggests primary hyperaldosteronism and warrants further confirmatory testing 1.
Before testing, it's essential to consider modifying medications that can affect results, such as spironolactone, eplerenone, and amiloride, which should be discontinued at least 4-6 weeks prior. ACE inhibitors, ARBs, and diuretics should be stopped 2 weeks before testing if possible. Beta-blockers can falsely elevate the ARR and should also be discontinued if clinically appropriate. The ARR is preferred as the initial test because it accounts for the physiological relationship between aldosterone and renin, providing better diagnostic accuracy than measuring either hormone alone in identifying this condition.
Some key points to consider when interpreting the ARR include:
- The patient 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serum potassium in the normal range, and mineralocorticoid receptor antagonists (e.g., spironolactone or eplerenone) withdrawn for at least 4 weeks before testing 1.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 plasma aldosterone concentration should be at least 10 ng/dL to interpret the test as positive 1.
- 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.
The diagnosis of primary aldosteronism generally requires a confirmatory test (intravenous saline suppression test or oral salt-loading test) 1. If the diagnosis of primary aldosteronism is confirmed, the patient is referred for an adrenal venous sampling procedure to determine whether the increased aldosterone production is unilateral or bilateral in origin. If unilateral aldosterone production is documented on adrenal venous sampling, the patient is referred for unilateral laparoscopic adrenalectomy, which improves BP in virtually 100% of patients and results in a complete cure of hypertension in about 50% 1.
It is crucial to follow the most recent guidelines for the management of primary hyperaldosteronism, as outlined in the 2024 ESC guidelines for the management of elevated blood pressure and hypertension 1. These guidelines recommend the ARR as the initial test for primary aldosteronism screening and provide guidance on the interpretation of the results and further evaluation.
In summary, the aldosterone-to-renin ratio (ARR) is the recommended initial lab test for primary hyperaldosteronism, and its interpretation should be guided by the most recent clinical guidelines and evidence-based practice 1.
From the Research
Initial Lab Test for Primary Hyperaldosteronism
The initial lab test for primary hyperaldosteronism (primary aldosterone excess) is the aldosterone-to-renin ratio (ARR) [ 2, 3, 4, 5, 6 ].
Key Points
- The ARR is a practical and informative initial test for primary hyperaldosteronism [ 2 ].
- An elevated aldosterone/renin ratio is confirmed, and then confirmatory tests should be performed [ 3 ].
- The aldosterone-to-renin ratio is an easy, inexpensive, and rapid means of screening for the disorder [ 5 ].
- The wider application of aldosterone/renin ratio as a screening test has substantially contributed to increasing diagnosis of PA [ 6 ].
Confirmatory Tests
After a positive screening test, the following confirmatory tests can be used: