What are the diagnostic criteria for primary hyperaldosteronism?

Diagnostic Criteria for Primary Hyperaldosteronism

The diagnosis of primary hyperaldosteronism requires a positive screening test (elevated aldosterone-to-renin ratio) followed by confirmatory testing demonstrating autonomous aldosterone hypersecretion that fails to suppress appropriately.

Screening Criteria

Who Should Be Screened

Screen patients with any of the following high-risk features 1, 2:

• Blood pressure ≥150/100 mm Hg on three separate measurements
• Resistant hypertension: BP >140/90 mm Hg despite three antihypertensive drugs (including a diuretic), or controlled BP requiring ≥4 medications
• Hypertension with spontaneous or diuretic-induced hypokalemia (though 72% of PA patients are normokalemic) 3
• Hypertension with adrenal incidentaloma
• Hypertension with sleep apnea
• Family history of early-onset hypertension or stroke at age <40 years
• All first-degree relatives of PA patients
• Hypertension onset at age ≤20 years 1, 2

Screening Test: Aldosterone-to-Renin Ratio (ARR)

The ARR is the preferred screening test and must be performed under standardized conditions 1, 2:

• Collect morning samples after patient sits for ≥15 minutes
• Correct hypokalemia before testing 4
• Medication management 1:
  • Withdraw for ≥4 weeks: aldosterone antagonists, angiotensin receptor blockers, ACE inhibitors, direct renin inhibitors, beta-blockers, clonidine
  • May continue: alpha-1 blockers, non-dihydropyridine calcium channel blockers, hydralazine
  • Women on oral contraceptives should discontinue for 1 month or use plasma renin activity instead of direct renin concentration 1

Positive screening thresholds (aldosterone in pmol/L) 1:

Renin Method	Higher Sensitivity Cut-off	Higher Specificity Cut-off
Plasma renin activity (ng/mL/h)	>555	>750
Direct renin concentration (mIU/L)	>60	>91
Direct renin concentration (ng/L)	>100	>144

Confirmatory Testing

After positive screening, proceed to confirmatory testing unless the patient has spontaneous hypokalemia with undetectable renin AND plasma aldosterone >550 pmol/L (>20 ng/dL)—in this specific scenario, no further confirmation is needed 1, 2.

Confirmatory Test Options (Perform at least one)

1. Intravenous Saline Infusion Test 1:

• Administer 2 L normal saline IV over 4 hours with patient recumbent
• Contraindicated in severe uncontrolled hypertension or heart failure
• Positive for PA: Post-infusion aldosterone >280 pmol/L
• Negative for PA: Aldosterone <140 pmol/L
• Indeterminate: 140-280 pmol/L

2. Oral Sodium Loading Test 1:

• Administer >200 mmol/day oral sodium (>5 g/day sodium; >12 g/day salt; >2 tsp/day) for 3 days
• Measure 24-hour urinary aldosterone from morning of day 3 to morning of day 4
• Positive for PA: Urinary aldosterone >33 nmol/day
• Negative for PA: <28 nmol/day

3. Captopril Challenge Test 1:

• Patient sits/stands for 1 hour, then administer 25-50 mg captopril orally
• Measure aldosterone and renin at baseline and 1-2 hours post-dose while seated
• Positive for PA: Aldosterone remains elevated (fails to suppress >30%) with suppressed renin
• Negative for PA: Aldosterone suppresses >30%

4. Highly Elevated ARR with High Aldosterone 1:

• ARR >1400 pmol/L/ng/mL/h (or >270 pmol/L/ng/L for direct renin) AND plasma aldosterone >440 pmol/L
• This combination alone confirms autonomous hypersecretion

5. Fludrocortisone Suppression Test 5:

• Oral sodium loading plus fludrocortisone 0.25 mg/day for 2 days
• Positive for PA: Plasma aldosterone ≥140 pmol/L in upright and/or supine positions

Important Caveats

• All confirmatory tests except captopril challenge risk inducing hypokalemia, fluid overload, and worsening hypertension 4
• For borderline results, repeat the initial test or perform a second confirmatory test 4
• Patients negative on both saline infusion AND captopril tests are at low risk for unilateral disease, while those positive on both are more likely to have unilateral aldosterone secretion 4

Subtype Classification (After Confirmation)

All patients with confirmed PA require adrenal CT scanning (3 mm contiguous cuts) or MRI as the initial imaging study to exclude large masses and assess for adenomas 1, 2.

For patients considering surgery, adrenal venous sampling (AVS) should be performed to reliably differentiate unilateral from bilateral aldosterone overproduction, as imaging alone frequently misclassifies disease 1, 2, 6:

• AVS is mandatory except in highly selected cases: age <35 years with marked PA, hypokalemia, and unilateral adenoma >1.0 cm on imaging 6
• AVS must be performed at experienced centers due to technical complexity 1, 2

Special Genetic Testing Indications 1, 3

Consider genetic testing for glucocorticoid-remediable aldosteronism (familial hyperaldosteronism type 1) if:

• Family history of PA or stroke at age ≤40 years, OR
• Hypertension onset at age ≤20 years with negative imaging

This condition responds to low-dose dexamethasone (0.25-1 mg daily) rather than standard PA treatment 3.

Diagnostic Pitfalls

• Do not rely on hypokalemia to screen for PA—approximately 72% of PA patients are normokalemic 3
• Do not skip confirmatory testing in most cases, as false-positive ARR occurs frequently 2, 4
• Do not proceed to surgery based on CT imaging alone without AVS, as nonfunctional adenomas are common and bilateral hyperplasia can be missed 1, 6
• Patients with positive ARR, normal/high aldosterone, low renin, but negative confirmatory testing may have mild hyperaldosteronism and still benefit from mineralocorticoid receptor antagonist therapy 4