This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Myasthenia Gravis and Muscular dystrophy, Subject name: Medicine
What is not useful for diagnosis of myasthenia gravis? 
Select and explain. 
A. AChR antibodies, B. Voltage gated calcium channel antibodies, C. Muscle-specific kinase antibodies, D. Edrophonium test
B: Voltage gated calcium channel antibodies
Answer: B: Voltage gated calcium channel antibodies 
Explanation: Voltage-gated calcium channel antibodies are used for diagnosis of Lambe Eaton syndrome. Choices A, C,and D are used for diagnosis of M. Gravis.