This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
The MOST sensitive 24 hour urinary biochemical test to suggest pheochromocytoma among the following is 
Select and explain. 
A. Vanillylmandelic acid, B. Fractionated metanephrines, C. Total metanephrines, D. Catecholamines
B: Fractionated metanephrines
Answer: B: Fractionated metanephrines 
Explanation: Table 343-2 Biochemical Tests Used for Pheochromocytoma Diagnosis Diagnostic Method Sensitivity Specificity 24-h urinary tests Vanillylmandelic acid ++ ++++ Catecholamines +++ +++ Fractionated metanephrines ++++ ++ Total metanephrines +++ ++++ Ref: Harrisons Principles of Internal Medicine, 18th Edition, Page 2963