A 38-year-old female presents with recurrent severe headaches, sweating episodes, and palpitations. On exam, her blood pressure is 210/115 mmHg and pulse is 112 bpm. Suspicion for pheochromocytoma is high. What is the most sensitive initial screening diagnostic test?
Answer and explanation
Correct answer: D. Plasma free metanephrines or 24-hour urinary fractionated metanephrines
- Step 1: Pheochromocytoma is a catecholamine-secreting tumor of chromaffin cells in the adrenal medulla.
- Step 2: Metanephrines (metanephrine and normetanephrine) are metabolites continuously produced within the tumor and released into plasma.
- Step 3: Fractionated plasma free metanephrines have high diagnostic sensitivity (97-99%) and represent the premier screening test of choice.
Answer
Plasma free metanephrines or 24-hour urinary fractionated metanephrines.
Why not the others: '24-hour urinary free cortisol excretion' screens for Cushing syndrome; 'Renal artery Doppler ultrasound' evaluates renal artery stenosis in renovascular hypertension; 'Serum aldosterone-to-renin ratio' screens for primary hyperaldosteronism (Conn syndrome).
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