Myasthenia gravis (MG) is characterised by muscle weakness & easy fatigability most commonly due to autoantibody mediated loss of functional acetylcholine receptors in the postsynaptic membrane of skeletal muscle. ACHR antibodies are not found in Congenital MG. This assay is used to diagnose Acquired forms of MG (90% positive), for detecting subclinical MG in recipients of D-penicillamine, Thymoma without clinical evidence of MG & Graft versus Host disease. It may also be positive in Lambert-Eaton myasthenic syndrome, Autoimmune liver disease & Paraneoplastic autoimmune neurological disorders.