Ppgl Confirmation Test Selection

---
name: ppgl-confirmation-test-selection
description: Selects the appropriate functional confirmation test after a positive PPGL screening test to establish biochemical diagnosis. Triggered by statements such as 'Screening test positive for PPGL,' 'Need to confirm PPGL diagnosis before imaging,' or 'Biochemical test results exceed screening thresholds.'
---

# PPGL Functional Confirmation Test Selection

## STEP 1 — Gather Information
Collect screening test modality and result (e.g., random urinary fractionated metanephrines/Cr, plasma-free fractionated metanephrines, or blood fractionated catecholamines), assess patient’s ability to complete a 24‑hour urine collection (continence, renal function, outpatient setting), and note local assay availability for metanephrines vs catecholamines.  
→ If 24‑hour urine collection is feasible, proceed to Step 2; if not feasible, skip to plasma‑free fractionated metanephrines (Step 4).

## STEP 2 — Rule In / Rule Out
First binary fork: Is 24‑hour urine collection possible?  
- **No** → Rule in plasma‑free fractionated metanephrines as the confirmation test; go to Step 4.  
- **Yes** → Rule out plasma‑free test for now; proceed to evaluate urinary options (Step 3).

## STEP 3 — Classify or Stratify
Among urinary tests, prioritize fractionated metanephrines (more stable, longer half‑life) if the assay is available; otherwise use fractionated catecholamines.  
→ Decision: order 24‑hour urinary fractionated metanephrines if assay accessible, else order 24‑hour urinary fractionated catecholamines.

## STEP 4 — Decide
Order the selected confirmation test with the appropriate diagnostic cutoff:  
- 24‑hour urinary fractionated metanephrines >3× ULN,  
- 24‑hour urinary fractionated catecholamines >2× ULN, or  
- plasma‑free fractionated metanephrines >ULN.  
Arrange specimen handling per lab requirements (acid‑protected urine, cold plasma separation within 30 min).

## Clinical Guardrails / Mimics / Pitfalls
Avoid false positives from stress, caffeine, tyramine‑rich foods, or tricyclic antidepressants; ensure proper urine acidification and plasma sample freezing within 30 min. Note that plasma‑free fractionated metanephrines are reimbursable only once under Japanese health insurance for differential diagnosis. Do not rely on random urine metanephrines/Cr for confirmation; it is a screening tool only.

## Concrete Clinical Example
A 48‑year‑old woman with an incidental adrenal nodule has a random urinary metanephrines/Cr ratio 4× ULN. She is continent and can collect urine locally. The lab offers metanephrine assay. Step 1 proceeds to Step 2 (urine feasible). Step 2 rules in urinary testing. Step 3 selects 24‑hour urinary fractionated metanephrines. Step 4 orders the test with a cutoff >3× ULN; result returns 9× ULN, confirming PPGL biochemical diagnosis.

**Source:** Clinical Practice Guideline for the Diagnosis and Management of Pheochromocytoma and Paraganglioma 2025, Japan Endocrine Society, 2025, doi:10.1507/endocrj.EJ25-0165