A 42-year-old woman presents with episodic headache, palpitations, sweating, and paroxysmal hypertension up to 240/140 mmHg between episodes. Which is the most sensitive initial biochemical test to confirm the suspected diagnosis?

• A Plasma free metanephrines ✓
• B 24-hour urinary vanillylmandelic acid
• C Serum cortisol after dexamethasone suppression
• D Plasma aldosterone-to-renin ratio

Explanation

The triad of episodic headache, sweating, and tachycardia with paroxysmal hypertension is classic for pheochromocytoma. Plasma free metanephrines have the highest sensitivity for screening at approximately 96 to 99 percent and are the recommended first-line test. Twenty-four-hour urinary catecholamines and metanephrines are also used but less sensitive than plasma free metanephrines. VMA is less sensitive and rarely used first. Plasma aldosterone-to-renin ratio screens for primary hyperaldosteronism. Dexamethasone suppression tests screen for Cushing syndrome.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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