Interpret Postural Stimulation Test for PA
STEP 1 — Gather Information
Measure supine plasma aldosterone concentration (PAC), then have the patient stand upright for at least 2 hours and measure PAC again; record age, family history of hypertension/stroke before age 40, presence of hypokalemia, and current medications (especially MR antagonists, ACEi/ARBs).
STEP 2 — Rule In / Rule Out
If upright PAC shows a significant rise (e.g., ≥2‑fold increase or >20 % absolute increase) compared with supine → angiotensin II‑responsive phenotype (rule out angiotensin II‑unresponsive subtypes). If upright PAC does not rise significantly → rule in angiotensin II‑unresponsive APA or FH‑I.
STEP 3 — Classify or Stratify
Among non‑responsive cases, assess for FH‑I: age <20 years, family history of early‑onset hypertension or stroke, or severe hypokalemia → suspect FH‑I and plan genetic testing; otherwise suspect angiotensin II‑unresponsive APA.
STEP 4 — Decide
If FH‑I suspected, order genetic testing for the CYP11B1/CYP11B2 chimeric gene (GRA) and consider low‑dose glucocorticoid therapy; if APA suspected, proceed to adrenal venous sampling (AVS) to confirm lateralization, or if AVS is unsuccessful, consider unilateral adrenalectomy based on a unilateral adrenal mass on CT.
Clinical Guardrails / Mimics / Pitfalls
Do not interpret the test in patients taking MR antagonists, ACE inhibitors, ARBs, or with severe uncontrolled hypertension, as these can blunt aldosterone response. Lack of aldosterone rise may also occur in idiopathic hyperaldosteronism (IHA) with diurnal variation; avoid confusing IHA with FH‑I without genetic confirmation. False‑negative results are possible if the standing period is insufficient or if the patient has recent sodium loading.
Concrete Clinical Example
A 22‑year‑old woman with hypertension, hypokalemia, and elevated ARR undergoes postural stimulation test: supine PAC 12 ng/dL, upright PAC 13 ng/dL (no significant rise). She has a brother diagnosed with hypertension at age 30. FH‑I is suspected; genetic testing confirms a CYP11B1/CYP11B2 chimera, and she is started on low‑dose dexamethasone.
Source: The Management of Primary Aldosteronism: Case Detection, Diagnosis, and Treatment: An Endocrine Society Clinical Practice Guideline, Endocrine Society, 2016, DOI:10.1210/jc.2015-4061