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Diagnose acquired myasthenia gravis1
This procedure may be considered by Medicare and other carriers as investigational and, therefore, may not be payable as a covered benefit for patients.
AChR antibody binding: Measures antibodies that precipitate solublized muscle AChR that has been complexed with radiolabeled alpha-bungarotoxin (αBTX). Antibodies that bind to the receptor regions that are not sterically blocked by the αBTX are detected.
AChR antibody blocking: Measures antibodies that inhibit the binding of radiolabeled alpha-bungarotoxin (αBTX) to solublized muscle AChR.
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
AChR blocking antibodies are observed in 52% of patients with autoimmune myasthenia gravis.1 These autoantibodies interfere with normal neuromuscular function, causing muscle weakness and fatigue. Approximately 1% of individuals are positive for AChR blocking antibodies in the absence of AChR binding antibodies.1
1 mL (Note: This volume does not allow for repeat testing.)
If a red-top tube is used, transfer separated serum to a plastic transport tube.
Causes for Rejection
|Order Code||Order Code Name||Order Loinc||Result Code||Result Code Name||UofM||Result LOINC|
|086120||Myasthenia Gravis Panel I||085904||AChR Binding Abs, Serum||nmol/L||11034-6|
|086120||Myasthenia Gravis Panel I||085927||AChR Blocking Abs, Serum||%||11561-8|