Repeat PA screening after withdrawing interfering medications if initial screen negative
STEP 1 — Gather Information
Collect morning seated serum/plasma aldosterone and plasma renin (concentration or activity), serum potassium, and medication list (including MRAs, ENaC inhibitors, ACE inhibitors, ARBs, beta-blockers, centrally acting alpha-agonists). Assess for hypokalemia, resistant hypertension, and pretest probability of PA.
STEP 2 — Rule In / Rule Out
Is the initial aldosterone-to-renin ratio (ARR) screen negative or positive?
STEP 3 — Classify or Stratify
If screen negative, evaluate for false-negative contributors: hypokalemia or use of MRAs, ENaC inhibitors, ACE inhibitors, ARBs. If screen positive, evaluate for false-positive contributors: use of beta-blockers or centrally acting alpha-agonists (clonidine, alpha-methyldopa) that suppress renin.
STEP 4 — Decide
For negative screen with false-negative contributors, correct potassium to lab reference range and withdraw interfering medications (4 weeks for MRAs/ENaC inhibitors, 2 weeks for ACE inhibitors/ARBs) if safe and feasible, then repeat ARR screen. For positive screen with false-positive contributors, withdraw beta-blockers or centrally acting alpha-agonists for 2 weeks if safe and feasible, then repeat ARR screen.
Clinical Guardrails / Mimics / Pitfalls
Do not rely on hypokalemia alone to exclude PA; do not repeat screening without correcting potassium or withdrawing medications when indicated; do not withdraw medications that are unsafe to stop (e.g., in heart failure) without cardiology input; do not assume a negative screen rules out PA in patients with moderate-to-high pretest probability; avoid repeating screen too soon before medication washout is complete.
Concrete Clinical Example
A 52-year-old with hypertension and hypokalemia (K+ 3.0 mmol/L) has an initial ARR of 15 (negative). She is taking spironolactone 25 mg daily for hypertension. After correcting potassium with supplementation and holding spironolactone for 4 weeks, repeat ARR is 35 (positive), leading to confirmatory testing and diagnosis of an aldosterone-producing adenoma.
Source: Primary Aldosteronism: An Endocrine Society Clinical Practice Guideline, Endocrine Society, 2025, https://doi.org/10.1210/clinem/dgaf284