Acetylcholine Receptor (AChR)-blocking Antibodies

CPT: 83519
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Test Details

Synonyms

  • AChR-blocking Antibodies
  • ACRAB
  • Anti-AChR Antibody
  • Myasthenia Gravis Antibody

Use

This assay is a secondary test for confirming the diagnosis of acquired myasthenia gravis.1

Limitations

AChR autoantibodies are not typically found in congenital myasthenia.

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

This assay measures antibodies that inhibit the binding of radiolabeled alpha-bungarotoxin (α-BTX) 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. 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

1 mL

Minimum Volume

0.3 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: ASM Press;2002:1005-1012.

References

Hara H, Hayashi K, Ohta K, Itoh N, Nishitani H, Ohta M. Detection and characterization of blocking-type anti-acetylcholine 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 (review). 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
085926 AChR Blocking Abs, Serum 11561-8 085927 AChR Blocking Abs, Serum % 11561-8

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