Aldosterone-to-renin Ratio

Labs

Aldosterone
ng/dL
Plasma renin activity
ng/mL/hr
Potassium
Optional
mEq/L

Possible Confounders

Current medication
Optional
Positive Test Reference
Parameter Threshold
Suppressed PRA ≤1 ng/mL/hr
Aldosterone ≥10 ng/dL
ARR >20
Borderline pattern PRA ≤1 with aldosterone 5–9.9 ng/dL

Primary Aldosteronism Decision Tree

1 Case Detection

Is the initial PA screen positive?

  • PRA ≤1 ng/mL/hr
  • Aldosterone ≥10 ng/dL
  • Supportive: ARR >20
No

Is potassium below the lower limit of normal?

Yes

Correct hypokalemia

Retest for primary aldosteronism after normokalemia is confirmed.

No

Is the patient taking a medication that raises renin?

  • MRA
  • ENaC inhibitor
  • Diuretic
Yes

Withdraw and repeat

Withdraw the interfering medication for 4 weeks and repeat testing when reasonable and safe.

If clinical suspicion is moderate to high and the medication cannot safely be withheld, an empiric trial of MRA therapy is reasonable.

No

Is either of the following present?

  • Suppressed renin with aldosterone 5 to <10 ng/dL
  • ACE inhibitor, ARB, or dihydropyridine CCB
No

Primary aldosteronism unlikely

Treat primary hypertension.

Yes

Clinical suspicion for PA?

No further PA testing

Treat as primary hypertension.

Repeat testing

Withdraw weakly interfering medications for 2 weeks before retesting when reasonable and safe.

If medication cannot safely be withheld, an empiric trial of MRA therapy is reasonable.

Yes

Primary aldosteronism likely

Continue to treatment and lateralization assessment.

2 Treatment & Lateralization

Are biochemical features of severe PA present?

All:
  • Spontaneous hypokalemia
  • PRA <0.2 ng/mL/hr
  • Aldosterone >20 ng/dL
Yes

High likelihood of lateralizing PA

Subtype classification is warranted for most patients.

Perform adrenal CT.

Are all of the following true?

  • Unilateral adrenal adenoma >1 cm and <2 cm
  • Age <35 years
  • Severe biochemical PA
Yes

Unilateral adrenalectomy reasonable

AVS may be performed first if available and additional confirmation of lateralizing PA is desired.

No

Are both of the following present?

  • Normokalemia
  • Aldosterone <11 ng/dL
Yes

Low likelihood of lateralizing PA

A trial of MRA therapy is reasonable for hypertension management.

No

Intermediate probability of lateralizing PA

MRA therapy or additional evaluation to pursue adrenalectomy are both reasonable options.

Interested in pursuing adrenalectomy?

No

Initiate MRA therapy

Yes

Perform aldosterone suppression testing

Are the results consistent with unsuppressible aldosterone production?

No

Initiate MRA therapy

Yes

Subtype classification

Perform adrenal CT, then proceed to AVS unless the young-patient exception applies.

Does AVS demonstrate lateralized aldosterone production?

Yes

Unilateral adrenalectomy

No

Initiate MRA therapy

Reference Criteria
Positive PA screen PRA ≤1 ng/mL/hr + aldosterone ≥10 ng/dL; ARR often >20
Borderline screen Suppressed PRA with aldosterone 5 to <10 ng/dL
Severe PA Spontaneous hypokalemia + PRA <0.2 ng/mL/hr + aldosterone >20 ng/dL
Low lateralization Normokalemia + aldosterone <11 ng/dL
4-week washout MRA, ENaC inhibitor, diuretic
2-week washout ACE inhibitor, ARB, dihydropyridine CCB when clinically appropriate