Avoid aldosterone suppression testing when PA likelihood is low

STEP 1 — Gather Information

• Confirm positive PA screening (elevated ARR with suppressed renin and inappropriate aldosterone)
• Measure serum potassium to assess for normokalemia (typically 3.5–5.0 mmol/L)
• Obtain aldosterone concentration and note assay method (immunoassay vs LC‑MS/MS)

STEP 2 — Rule In / Rule Out

• Is the patient normokalemic and is aldosterone < 11 ng/dL (immunoassay) or < 8 ng/dL (LC‑MS/MS)?
  • Yes → Proceed to Step 3 (low likelihood)
  • No → Do not avoid testing; consider aldosterone suppression testing if intermediate probability for lateralizing PA and surgical interest

STEP 3 — Classify or Stratify

• Classify as low likelihood of lateralizing PA when both normokalemia and aldosterone below cutoff are present
• Otherwise classify as intermediate or high likelihood (requires further testing)

STEP 4 — Decide

• If low likelihood: avoid aldosterone suppression testing and initiate empiric MRA therapy based on screening results
• If not low likelihood: proceed to aldosterone suppression testing (or other workup) per guideline

Clinical Guardrails / Mimics / Pitfalls

• Do not rely solely on hypokalemia; up to 60 % of PA patients are normokalemic
• Avoid false reassurance: ensure ARR elevation is genuine (exclude spurious aldosterone elevation from medications, posture, or acute stress)
• Do not use this rule in patients with resistant hypertension, hypokalemia, or overt biochemical evidence of renin‑independent aldosterone production (PRA < 0.2 ng/mL/h or DRC < 2 mU/L with aldosterone > 15 ng/dL immunoassay or > 20 ng/dL LC‑MS/MS)
• Remember that familial hyperaldosteronism and young‑onset PA (<20 yr) also warrant avoidance of suppression testing via genetic screening, not this rule

Concrete Clinical Example

A 58‑year‑old with hypertension has ARR = 45, renin = 0.3 ng/mL/h, aldosterone = 9 ng/dL by immunoassay, potassium = 4.2 mmol/L. Normokalemic and aldosterone < 11 ng/dL → low likelihood → avoid suppression trial, start spironolactone 25 mg daily.

Source: Primary Aldosteronism: An Endocrine Society Clinical Practice Guideline, Endocrine Society, 2025, https://doi.org/10.1210/clinem/dgaf284

TODO: consider adding scripts/calc.py for the endo-avoid-aldosterone-suppression-test calculator