- Prepare the patient first: correct hypokalemia, allow a liberal (unrestricted) sodium intake, and account for interfering drugs (see Pearls). Draw the sample mid-morning, after the patient has been up for 2 hours and seated for 5–15 minutes.
- Enter the plasma aldosterone concentration (PAC) and pick its unit (ng/dL or pmol/L — pmol/L is auto-converted).
- Choose the renin measure — plasma renin activity (PRA) in ng/mL/hr, or direct renin concentration (DRC) in mU/L or ng/L — and enter the value. The ARR and screen result update automatically.
- A positive screen needs both an elevated ratio and an elevated absolute aldosterone (PAC ≥ 15 ng/dL). Cutoffs are assay-dependent; confirm with your laboratory.
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When to Use
Use the ARR to screen for primary aldosteronism in patients at higher pre-test probability. The Endocrine Society recommends case detection in: sustained BP > 150/100 on three readings; resistant hypertension (BP above goal on three drugs including a diuretic, or controlled on ≥4 drugs); hypertension with spontaneous or diuretic-induced hypokalemia; hypertension with an adrenal incidentaloma; hypertension with obstructive sleep apnea; early-onset hypertension or stroke at a young age; and any hypertensive patient with a first-degree relative with primary aldosteronism. The ARR is a screening test only — a positive result must be confirmed before subtype workup.
Appropriate population
Adults with hypertension and one or more of the above risk features. Screening is worthwhile because primary aldosteronism is common (an appreciable share of resistant hypertension) and is the most frequent potentially curable / specifically treatable form of secondary hypertension — unilateral disease may be cured surgically, and bilateral disease responds to mineralocorticoid-receptor antagonists.
When the result can mislead
Interpret the ARR only when preparation is adequate. Hypokalemia suppresses aldosterone and can cause a false-negative — correct potassium first. Sodium restriction raises renin and can lower the ratio (false-negative). Many antihypertensives shift the ratio: mineralocorticoid-receptor antagonists (spironolactone, eplerenone) and high-dose amiloride can mask disease and should be stopped ~4–6 weeks before testing; beta-blockers and central α-agonists raise the ARR (false-positives); ACE inhibitors, ARBs, direct renin inhibitors, and diuretics lower it (false-negatives). The cutoffs are assay- and lab-specific — always anchor to your laboratory's reference values.
Pearls & Pitfalls
The ratio AND the absolute aldosterone
A high ARR alone is not enough. Because the ratio rises sharply when renin is very low, a suppressed renin can inflate the ARR even when aldosterone is not truly elevated. The Endocrine Society therefore pairs the ratio with a minimum aldosterone threshold — typically PAC ≥ 15 ng/dL (some centers use ≥ 10 ng/dL by immunoassay). Require both an elevated ratio and an elevated absolute aldosterone before calling a screen positive.
Cutoffs are assay-dependent
With aldosterone in ng/dL: ARR (PAC ÷ PRA) cut-points commonly used are around 20–30 (ng/dL per ng/mL/hr) — ~20 with immunoassay aldosterone, ~30 in many labs. For direct renin concentration, ARR (PAC ng/dL ÷ DRC mU/L) cut-points run roughly 2.0–3.8 (assay-dependent). As a rough conversion, DRC (mU/L) ≈ PRA (ng/mL/hr) × 8.2. Always confirm the threshold your laboratory validated; do not transplant a number across assays.
Pitfalls
(1) A positive ARR is a screen, not a diagnosis — it must be confirmed (saline infusion, captopril challenge, fludrocortisone suppression, or oral salt loading) before adrenal CT and adrenal vein sampling. (2) Test in the right conditions: correct hypokalemia, liberal sodium, mid-morning ambulant sample. (3) Drugs interfere: MRAs / high-dose amiloride mask disease (stop ~4–6 weeks); beta-blockers raise the ARR (false-positive); ACEi/ARB/renin inhibitors/diuretics lower it (false-negative) — verapamil-SR, hydralazine, doxazosin/prazosin are the least-interfering agents for BP control during testing. (4) A detectable/high renin with a high ARR argues against primary aldosteronism — recheck for interfering drugs or analytic error.
Why Use It
Primary aldosteronism is far more common than once believed — it accounts for a substantial fraction of resistant hypertension and a meaningful share of all hypertension — yet it is profoundly underdiagnosed. Untreated, the inappropriate aldosterone excess drives target-organ damage out of proportion to the blood pressure: more atrial fibrillation, stroke, heart failure, and kidney injury than matched essential hypertensives. Crucially it is specifically treatable: unilateral disease can be cured by adrenalectomy, and bilateral disease responds to mineralocorticoid-receptor antagonists. The ARR is the validated, inexpensive first-line screen that opens this diagnostic pathway. Because so few eligible patients are ever screened, a low threshold to calculate the ARR in the right population is one of the highest-yield actions in the hypertension clinic.
Aldosterone-Renin Ratio (ARR) — Primary Aldosteronism Screening
Enter the plasma aldosterone (PAC) and a renin measure to compute the ARR and a provisional screen result. Cutoffs are assay-dependent — this tool uses the commonly cited Endocrine Society thresholds and pairs the ratio with a minimum aldosterone of PAC ≥ 15 ng/dL. Always confirm against your laboratory's validated cut-points, and remember a positive screen requires a confirmatory test.
⚕ Cutoffs per Funder JW et al, Endocrine Society Clinical Practice Guideline, J Clin Endocrinol Metab 2016;101(5):1889–1916. ARR cut-points are assay- and laboratory-dependent; this tool flags a positive screen when the ratio exceeds the commonly used threshold (ARR ≥ 30 for PAC ng/dL ÷ PRA; ≥ 3.8 for PAC ng/dL ÷ DRC mU/L) and PAC ≥ 15 ng/dL. A positive screen requires a confirmatory test before subtype workup. Ensure hypokalemia is corrected, sodium intake liberal, and interfering drugs accounted for. For licensed clinicians; not a substitute for individualized assessment.
Next Steps
Use the screen result to decide whether to proceed to confirmatory testing.
- Positive screen (elevated ARR and PAC ≥ 15 ng/dL): proceed to a confirmatory test — saline infusion test, captopril challenge, fludrocortisone suppression, or oral salt loading — to confirm autonomous aldosterone secretion. Most patients with an unequivocally positive screen and spontaneous hypokalemia with undetectable renin may proceed without further confirmation per the guideline.
- If confirmed: move to subtype classification — adrenal CT to exclude carcinoma, then adrenal vein sampling (AVS) in surgical candidates to distinguish unilateral (adenoma — adrenalectomy) from bilateral (hyperplasia — mineralocorticoid-receptor antagonist) disease.
- Indeterminate / borderline: review preparation (potassium, sodium, posture, timing) and interfering drugs, switch to least-interfering agents (verapamil-SR, hydralazine, doxazosin/prazosin) if needed, and repeat.
- Negative screen: primary aldosteronism is unlikely, but recheck if a false-negative is plausible (sodium restriction, hypokalemia, ACEi/ARB/diuretic/renin-inhibitor use). Continue standard blood-pressure management and reassess overall cardiovascular risk.
Evidence & References
Formula
| Quantity | Formula |
|---|---|
| ARR (with PRA) | PAC (ng/dL) ÷ PRA (ng/mL/hr) |
| ARR (with DRC) | PAC (ng/dL) ÷ DRC (mU/L) |
| PAC unit conversion | PAC (ng/dL) = PAC (pmol/L) ÷ 27.7 |
| Renin conversion (approx.) | DRC (mU/L) ≈ PRA (ng/mL/hr) × 8.2 |
Commonly used cut-points (assay-dependent)
| Denominator | Positive screen (typical) |
|---|---|
| PAC (ng/dL) ÷ PRA (ng/mL/hr) | ARR ≥ 20–30 and PAC ≥ 15 ng/dL |
| PAC (ng/dL) ÷ DRC (mU/L) | ARR ≥ 2.0–3.8 and PAC ≥ 15 ng/dL |
The Endocrine Society guideline emphasizes that the ARR is highly assay- and laboratory-dependent and that most authorities pair the ratio with a minimum aldosterone concentration (commonly PAC ≥ 15 ng/dL) to limit false-positives driven by very low renin. The ARR is a case-detection (screening) test; a positive result requires a confirmatory test before subtype workup. Sample under standardized conditions: hypokalemia corrected, unrestricted sodium, mid-morning ambulant draw, and interfering drugs withdrawn or substituted.
References
- Funder JW, Carey RM, Mantero F, et al. The management of primary aldosteronism: case detection, diagnosis, and treatment — an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2016;101(5):1889–1916. doi:10.1210/jc.2015-4061.
- Williams TA, Lenders JWM, Mulatero P, et al. Outcomes after adrenalectomy for unilateral primary aldosteronism: an international consensus on outcome measures and analysis of remission rates in an international cohort (PASO study). Lancet Diabetes Endocrinol. 2017;5(9):689–699.
- Whelton PK, Carey RM, Aronow WS, et al. 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. Hypertension. 2018;71(6):e13–e115.
