Myasthenia Gravis Profile I

CPT: 83519(x2)
Print Share

Test Details

Test Includes

AChR-binding antibodies; AChR-blocking antibodies

Use

Diagnose acquired myasthenia gravis1

Limitations

This procedure may be considered by Medicare and other carriers as investigational and, therefore, may not be payable as a covered benefit for patients.

Methodology

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.

Additional Information

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

Specimen Requirements

Specimen

Serum

Volume

2 mL

Minimum Volume

1 mL (Note: This volume does not allow for repeat testing.)

Container

Red-top tube or gel-barrier tube

Patient Preparation

No isotopes administered 24 hours prior to venipuncture

Collection

If a red-top tube is used, transfer separated serum to a plastic transport tube.

Storage Instructions

Refrigerate

Stability Requirements

Temperature

Period

Room temperature

13 days

Refrigerated

13 days

Frozen

13 days

Freeze/thaw cycles

Stable x3

Causes for Rejection

Excessive hemolysis; chylous serum; recently administered isotopes; plasma specimen

Clinical Information

Footnotes

1. Griesmann GE, Kryzer TJ, Lennon VA. Autoantibody profiles of myasthenia gravis and Lambert-Eaton myasthenic syndrome. In: Rose NR, Hamilton RG, Detrick B, eds. Manual of Clinical Laboratory Immunology. 6th ed. Washington DC: AMS Press; 2002:1005-1012.

References

Hara H, Hayashi K, Ohta K, Itoh N, Nishitani H, Ohta M. Detection and characterization of blocking-type antiacetylcholine receptor antibodies in sera from patients with myasthenia gravis. Clin Chem. 1993 Oct; 39(10):2053-2057. 8403390
Protti MP, Manfredi AA, Horton RM, Bellone M, Conti-Tronconi BM. Myasthenia gravis; Recognition of a human autoantigen at the molecular level. Immunol Today. 1993 Jul; 14(7):363-368. 8363727
Vincent A, Newsom-Davis J. Acetylcholine receptor antibody as a diagnostic test for myasthenia gravis: Results in 153 validated cases and 2967 diagnostic assays. J Neurol Neurosurg Psychiatry. 1985 Dec; 48(12):1246-1252. 4087000
Wu JT, Astill M, Lloyd C, Salmon VC. Rhabdomyosarcoma cell line can be used for the isolation of soluble acetylcholine receptor and for assaying blocking and modulating autoantibodies. J Clin Lab Anal. 1993; 7(1):11-18. 8426270

LOINC® Map

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

For Providers

Please login to order a test.

 

© 2017  Laboratory Corporation of America® Holdings and Lexi-Comp Inc. All Rights Reserved.

CPT Statement/Profile Statement

The LOINC® codes are copyright © 1994-2017, Regenstrief Institute, Inc. and the Logical Observation Identifiers Names and Codes (LOINC) Committee. Permission is granted in perpetuity, without payment of license fees or royalties, to use, copy, or distribute the LOINC® codes for any commercial or non-commercial purpose, subject to the terms under the license agreement found at https://loinc.org/license/. Additional information regarding LOINC® codes can be found at LOINC.org, including the LOINC Manual, which can be downloaded at LOINC.org/downloads/files/LOINCManual.pdf