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In vitro diagnostic semiquantitative determination of autoantibodies against the acetylcholine receptor in human serum and plasma. This assay is the primary test for confirming the diagnosis of acquired myasthenia gravis.1
Antibodies are not found in congenital myasthenia.
Myasthenia gravis is an acquired disorder of neuromuscular transmission characterized by use-associated muscle weakness and fatigability.1 This condition frequently involves the extraocular muscles and has a strong association with tumor of the thymus (thymoma). The disease has a prevalence of approximately 5 per 100,000 individuals and can occur at any age. In women, the disease usually presents between the ages of 20 and 40 years, while disease onset in men typically occurs later in life.
Autoantibodies to postsynaptic acetylcholine receptors are detectable in the serum of 90% of patients with generalized myasthenia gravis and approximately 70% of patients with ocular myasthenia.1 These autoantibodies interfere with normal neuromuscular function, causing muscle weakness and fatigue. Antibody titers tend to be higher in females and a correlation between antibody titer and degree of muscle weakness has been observed in individual patients. Receptor antibody titers tend to rise several weeks before exacerbations in patients with established myasthenia gravis. Remission after thymectomy is associated with a progressive decline in antibody titers. Consequently, serial measurements of acetylcholine receptor antibodies can be useful in monitoring disease progression as well as the effects of treatment. (Myasthenia gravis is often associated with striational antibody.) AChR-binding antibodies can also be positive in uncomplicated thymoma, Lambert-Eaton myasthenic syndrome, primary lung cancer, and in patients with autoimmune liver disease.1
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