A 35-year-old woman presents with episodic headaches, palpitations, and excessive sweating. She has a history of resistant hypertension requiring multiple medications. Her blood pressure is currently 170/100 mmHg. Physical examination reveals a thin woman with mild tachycardia. Complete blood count, electrolytes, and renal function are normal. Which of the following is the most appropriate initial diagnostic test?
✓ Correct Answer: Option B
The constellation of paroxysmal hypertension, headaches, palpitations, and sweating is highly suggestive of pheochromocytoma, a catecholamine-secreting tumor. The most appropriate initial diagnostic test involves measuring plasma free metanephrines or 24-hour urinary fractionated metanephrines.