<prompt> Investigation of choice for myasthenia gravis?Single Fiber E.M.GMuscle biopsyNerve conduction velocityAnti -acetylcholine receptor antibody  <response>: Ans. a Single Fiber E.M.GRef: Harrison 19th ed. 442e-6 Single fiber E.M.G is the investigation of choice for myasthenia gravis and shows a decremental response Anti-acetylcholine receptor blocking antibody TITER is the most specific test for diagnosis of myasthenia gravis. Also remember that Tensilon test is a screening test for myasthenia gravis. False positive tensilon test can be seen in motor neuron disease. 