<prompt> Which one of the following is the most sensitive test for the diagnosis of myasthenia gravis?Elevated serum ACh-receptor binding antibodiesRepetitive nerve stimulation testPositive edrophonium testMeasurement of jitter by single fibre electromyography  <response>: Diagnosis of myasthenia gravis MG History:--diplopia, ptosis, weakness, fluctuation, and fatigue, worse with activity, improved by rest Physical examination:--ptosis, diplopia, motor power survey--quantitative testing of muscle strength, forward arm abduction time 5 min, vital capacity, the absence of other neurologic signs. Laboratory testing:--anti-AChR radioimmunoassay--85 positive in generalized MG, 50 in ocular MG, the definite diagnosis of positive; negative results do not exclude MG, 40 of AChR antibody-negative patients with generalized MG have anti-muscle antibodies. Repetitive nerve stimulation, the decrement of15 at 3Hz: highly probable. Single fiber electromyography: blocking and fitter, with normal fiber density; confirmatory, but not specific. Endorphin chloride--Tensile 2 mg 8 mg IV: highly probable diagnosis if unequivocal positive. For ocular or cranial MG, exclude intracranial lesions by CT or MRI. Ref - Harrisons internal medicine 20e pg 3233-3235, 3234t, 3237t 