A 39-year-old woman has recurrent episodes of pounding headache, drenching sweats, palpitations, and pallor lasting 15 to 30 minutes. Between episodes she is well and BP recorded during an attack was 230/125 mmHg. Which is the SINGLE best initial screening test?

• A Plasma renin activity
• B 24-hour urinary vanillylmandelic acid
• C Random plasma cortisol
• D Plasma fractionated free metanephrines ✓

Explanation

Paroxysms of headache, sweating and palpitations with extreme hypertension suggest pheochromocytoma. Plasma fractionated free metanephrines have the highest sensitivity and are the recommended first-line screening test, especially valuable between paroxysms. Urinary vanillylmandelic acid has poor sensitivity and specificity and is obsolete for screening. Cortisol and renin screen for other secondary causes and would both be expected here to be normal or nonspecifically altered.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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