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Test Code ACRAB Acetylcholine Receptor (AChR)-binding Antibodies

Important Note

Sunrise Clinical Manager (SCM) Orderable:

Acetylcholine Receptor Binding Antibody 

AllScripts (AEHR) Orderable: 

Acetylcholine Receptor Binding Antibody

 

Performing Laboratory

LabCorp Burlington, NC

Methodology

This assay 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.

Reference Values

Negative: 0.00−0.24 nmol/L

 Borderline: 0.25−0.40 nmol/L

 Positive: >0.40 nmol/L

Test Classification and CPT Coding

83519

 

LOINC: 11034-6

Specimen Requirements

Container/Tube:  Gold-top tube(s)

Specimen:  1 mL of serum(0.3 mL min)

                       No isotopes administered 24 hours prior to venipuncture

Transport Temperature:  Refrigerate

Stability:  14 days Room Temperature, Refrigerated, Frozen

Rejection: Gross hemolysis; gross icterus; gross lipemia

                

Computer Interface Code

PDM #  5901700

Useful For

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.

 

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

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.