Esa Pa Interpret Cct

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name: esa-pa-interpret-cct
description: Evaluates likelihood of primary aldosteronism by measuring plasma aldosterone suppression after oral captopril; normal suppression ≥30% makes PA unlikely, while lack of suppression with persistently suppressed plasma renin activity suggests PA. Use when assessing captopril challenge test (CCT) results for PA diagnosis in patients with positive aldosterone-to-renin ratio.
---

# Interpret Captopril Challenge Test for PA

## STEP 1 — Gather Information
- Measure baseline plasma aldosterone concentration (PAC) and plasma renin activity (PRA) after seated/standing ≥1h, ensuring medications that affect the ARR (ACEi, ARBs, diuretics, MR antagonists) have been withdrawn per guideline Table 5.
- Administer 25–50 mg captopril orally.
- Draw blood for PAC, PRA, and cortisol at 0 h and 1–2 h post‑dose, keeping the patient seated during the interval.

## STEP 2 — Rule In / Rule Out
- If PAC decreases by **≥30%** from baseline → **PA unlikely** (normal captopril response).  
- If PAC decreases by **<30%** and PRA remains suppressed → **proceed** to further stratification (possible PA).  
- If PAC decreases <30% but PRA is not suppressed → test indeterminate; consider alternative causes.

## STEP 3 — Classify or Stratify
- Among non‑suppressed cases, assess degree of aldosterone change:  
  - **Some suppression (0 % < ΔPAC < 30 %)** → favors idiopathic adrenal hyperplasia (IAH).  
  - **No suppression or rise (ΔPAC ≤ 0 %)** → favors aldosterone‑producing adenoma (APA).  

## STEP 4 — Decide
- **IAH‑suggestive pattern**: consider saline infusion test or fludrocortisone suppression test for confirmation.  
- **APA‑suggestive pattern**: proceed to adrenal venous sampling for lateralization and potential unilateral adrenalectomy.  
- **PA unlikely**: investigate other causes of hypertension; do not pursue PA‑specific work‑up.

## Clinical Guardrails / Mimics / Pitfalls
- Do not interpret CCT if patient is on ACE inhibitors, ARBs, potassium‑wasting/sparing diuretics, MR antagonists, or NSAIDs without adequate washout (see Table 5).  
- Avoid in severe uncontrolled hypertension, hypokalemia, or congestive heart failure due to altered aldosterone dynamics.  
- False‑negative/equivocal results occur in up to ~30 % of cases; a non‑suppressive CCT alone does not confirm PA.  
- Ensure seated posture and adequate sodium intake; recumbent posture or sodium restriction can blunt the test response.

## Concrete Clinical Example
A 58‑year‑old with resistant hypertension (BP 168/96 mm Hg) has baseline PAC 22 ng/dL, PRA 0.18 ng/mL/h. After 50 mg captopril, PAC falls to 16 ng/dL (27 % suppression) and PRA remains 0.09 ng/mL/h. Because suppression is <30 % and PRA stays suppressed, PA is suspected; subsequent AVS shows lateralization consistent with an aldosterone‑producing adenoma, leading to laparoscopic adrenalectomy.

**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