Acetylcholine Receptor (AChR)-blocking Antibodies

CPT: 86042
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  • AChR-blocking Antibodies
  • Anti-AChR Antibody
  • Myasthenia Gravis Antibody

Expected Turnaround Time

3 - 7 days

Related Documents

Specimen Requirements




1 mL

Minimum Volume

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


Red-top tube or gel-barrier tube


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

Storage Instructions


Stability Requirements



Room temperature

13 days


13 days


13 days

Freeze/thaw cycles

Stable x3

Patient Preparation

No isotopes administered 24 hours prior to venipuncture

Causes for Rejection

Gross hemolysis; gross icterus; gross lipemia

Test Details


Measurement of Acetylcholine Receptor (AChR)-blocking Antibodies in serum


This test was developed and its performance characteristics determined by Labcorp. It has not been cleared or approved by the Food and Drug Administration.

In rare cases AChR antibodies can be found in patients with other autoimmune disorders or with thymoma without MG.1

The causative autoantibody cannot be identified in up to 10 percent of patients with MG.


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

Additional Information

Myasthenia gravis (MG) is an acquired disorder of neuromuscular transmission that is characterized by skeletal muscle weakness and fatigability on exertion that is exacerbated by repeated muscle activity.2-7 This autoimmune disease is caused by antibodies directed toward receptors embedded in the motor endplate of the neuromuscular junction. Progressive weakness of the ocular muscles manifesting as asymmetric ptosis and variable diplopia are the presenting symptoms in 60% of patients.5,7 Many patients progress to more generalized weakness of peripheral limb muscles and muscles required for body posture, including facial and neck muscles. Bulbar muscle weakness compromises speaking (dysarthria), chewing and swallowing (dysphagia) and respiratory muscle weakness can lead to a myasthenic crisis where patients need to be ventilated artificially.8 Clinical symptoms may be restricted to one muscle group, in particular the eye muscles (ocular MG), or may become generalized (generalized MG).5-8

Patients with MG frequently have thymic abnormalities (thymic hyperplasia or thymoma).9 Ten to 15 percent of patients with MG patients have thymoma, and up to 50% of thymoma patients develop MG.9 It is thought that the thymus plays a role in MG pathogenesis and these patients respond well to the surgical removal of the thymus gland.10

Neonatal MG can occur as a result of trans-placental transit of antibodies from an affected mother to the fetus, or in some cases, due to antibody to the fetal form of AChR.11-13 In the latter case, the mother may be unaffected. It should be noted that the AChR antibody assays employed by Labcorp contain a mixture of adult and embryonic AChRs allowing for the detection of autoantibodies to both proteins. In most cases affected babies are born with a diminished ability to suck and generalized hypotonia. Decrease in utero feta movement caused by MG can also result in arthrogryposis multiplex congenital, a condition where the neonate suffers from contractures in more than two joints and in multiple body areas.

The majority of patients with MG have antibodies to the acetylcholine receptor (AChR) and, less frequently, to the other proteins at postsynaptic membrane of the neuromuscular junction.14-16 AChR antibodies impede neuromuscular transmission by a range of pathogenic mechanisms including the alteration of tissue architecture and/or by causing a reduction the density of functionality of AChRs.1,17-21 Three functionally different types of antibodies against muscle AChR can be measured.1,21-24

• AChR binding antibodies attach to the AChR activate the complement system result in in destruction and focal lysis of the neuromuscular junction leading to the destruction of AChR and AChR-related protein at the end-plate.1,20

• AChR blocking antibodies functionally block the binding of the neurotransmitter acetylcholine to the receptor.20 These antibodies usually occur in association with AChR-binding antibodies and have a higher prevalence in generalized MG compared with ocular MG.20

• AChR modulation antibodies crosslink receptor subunits in such as way as to cause the receptors to be internalized and degraded in a process known as antigenic modulation.20,22,25-27 Modulating antibodies are implicated with an increased risk of thymoma and the majority of patients with thymoma have modulating antibodies.28

Test for serum autoantibodies are highly sensitive and specific for generalized MG but lack sensitivity when there is pure ocular involvement.1,14,29-30 Approximately 85% of patients with generalized MG have detectable muscle AChR antibodies (of one or more types), while fewer patients with ocular MH have the antibodies (50-60%).4,30 In general, an elevated level of any one of the AChR-binding antibodies in a patient with compatible clinical features confirms the diagnosis of MG. Approximately 15 percent of individuals with confirmed myasthenia gravis have no measurable AChR binding, blocking, or modulating antibodies. Thirty-five percent of these patients (six percent of all MG patients) will have antibodies directed against a muscle-specific tyrosine kinase (MuSK).10,31 Autoantibodies levels do not generally correlate with disease severity. However, in individual patients, serial antibody titers tend to correlate with disease status.18,19,32-34

Autoantibodies directed against the contractile elements of striated muscle are found in 30% of adult patients with myasthenia gravis and in 80% of those with thymoma.35-37 Striational antibodies are associated with the late-onset MG subgroup and are rarely found in AChR antibody-negative MG.


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2. Berrih-Aknin S, Le Panse R. Myasthenia gravis: a comprehensive review of immune dysregulation and etiological mechanisms. J Autoimmun. 2014 Aug;52:90-100.24389034
3. Verschuuren JJ, Huijbers MG, Plomp JJ, et al. Pathophysiology of myasthenia gravis with antibodies to the acetylcholine receptor, muscle-specific kinase and low-density lipoprotein receptor-related protein 4. Autoimmun Rev. 2013 Jul;12(9):918-923.23535160
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6. Hehir MK, Silvestri NJ. Generalized Myasthenia Gravis: Classification, Clinical Presentation, Natural History, and Epidemiology. Neurol Clin. 2018 May;36(2):253-260.29655448
7. Juel VC, Massey JM. Myasthenia gravis. Orphanet J Rare Dis. 2007 Nov 6;2:44.17986328
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9. Bernard C, Frih H, Pasquet F, et al. Thymoma associated with autoimmune diseases: 85 cases and literature review. Autoimmun Rev. 2016 Jan;15(1):82-92.26408958
10. Randomized Trial of Thymectomy in Myasthenia Gravis. Published Erratum. N Engl J Med. 2017 May 25;376(21):2097.28471717
11. Gilhus NE. Myasthenia Gravis Can Have Consequences for Pregnancy and the Developing Child. Front Neurol. 2020 Jun 12;11:554.32595594
12. Midelfart Hoff J, Midelfart A. Maternal myasthenia gravis: a cause for arthrogryposis multiplex congenita. J Child Orthop. 2015 Dec;9(6):433-435.26482518
13. Riemersma S, Vincent A, Beeson D, et al. Association of arthrogryposis multiplex congenita with maternal antibodies inhibiting fetal acetylcholine receptor function. J Clin Invest. 1996 Nov 15;98(10):2358-2363.8941654
14. Vincent A. Unravelling the pathogenesis of myasthenia gravis. Nat Rev Immunol. 2002 Oct;2(10):797-804.12360217
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16. Zisimopoulou P, Evangelakou P, Tzartos J, et al. A comprehensive analysis of the epidemiology and clinical characteristics of anti-LRP4 in myasthenia gravis. J Autoimmun. 2014 Aug;52:139-14524373505
17. Conti-Fine BM, Diethelm-Okita B, Ostlie N, et al. Immunopathogenesis of myasthenia gravis. In: Kaminski HJ, ed. Myasthenia Gravis and Related Disorders. 2nd ed. New York, NY: Humana; 2009:43-70.
18. Andreetta F, Rinaldi E, Bartoccioni E, et al. Diagnostics of myasthenic syndromes: detection of anti-AChR and anti-MuSK antibodies. Neurol Sci. 2017 Oct;38(Suppl 2):253-257.29030770
19. Paz ML, Barrantes FJ. Autoimmune Attack of the Neuromuscular Junction in Myasthenia Gravis: Nicotinic Acetylcholine Receptors and Other Targets. ACS Chem Neurosci. 2019 May 15;10(5):2186-2194.30916550
20. Conti-Fine BM, Milani M, Kaminski HJ. Myasthenia gravis: past, present, and future. J Clin Invest. 2006 Nov;116(11):2843-2854.17080188
21. Koneczny I, Herbst R. Myasthenia Gravis: Pathogenic Effects of Autoantibodies on Neuromuscular Architecture. Cells. 2019 Jul 2;8(7):671.31269763
22. Howard FM Jr, Lennon VA, Finley J, Matsumoto J, Elveback LR. Clinical correlations of antibodies that bind, block, or modulate human acetylcholine receptors in myasthenia gravis. Ann N Y Acad Sci. 1987;505:526-538.3479935
23. Kang SY, Oh JH, Song SK, Lee JS, Choi JC, Kang JH. Both binding and blocking antibodies correlate with disease severity in myasthenia gravis. Neurol Sci. 2015 Jul;36(7):1167-1171.25964166
24. Keefe D, Hess D, Bosco J, et al. A rapid, fluorescence-based assay for detecting antigenic modulation of the acetylcholine receptor on human cell lines. Cytometry B Clin Cytom. 2009 May;76(3):206-212.18825779
25. Beeson D, Jacobson L, Newsom-Davis J, Vincent A. A transfected human muscle cell line expressing the adult subtype of the human muscle acetylcholine receptor for diagnostic assays in myasthenia gravis. Neurology. 1996 Dec;47(6):1552-1555.8960744
26. Lyons BW, Wu LL, Astill ME, Wu JT. Development of an assay for modulating anti-acetylcholine receptor autoantibodies using human rhabdomyosarcoma cell line. J Clin Lab Anal. 1998;12(5):315-319.9773965
27. Lozier BK, Haven TR, Astill ME, Hill HR. Detection of acetylcholine receptor modulating antibodies by flow cytometry. Am J Clin Pathol. 2015 Feb;143(2):186-912.25596244
28. Pascuzzi RM. Pearls and pitfalls in the diagnosis and management of neuromuscular junction disorders. Semin Neurol. 2001 Dec;21(4):425-440.11774058
29. Benatar M. A systematic review of diagnostic studies in myasthenia gravis. Neuromuscul Disord. 2006 Jul;16(7):459-467.16793269
30. Leite MI, Waters P, Vincent A. Diagnostic use of autoantibodies in myasthenia gravis. Autoimmunity. 2010 Aug;43(5-6):371-379.20380582
31. Guptill JT, Sanders DB, Evoli A. Anti-MuSK antibody myasthenia gravis: clinical findings and response to treatment in two large cohorts. Muscle Nerve. 2011 Jul;44(1):36-40.21674519
32. Peeler CE, De Lott LB, Nagia L, Lemos J, Eggenberger ER, Cornblath WT. Clinical Utility of Acetylcholine Receptor Antibody Testing in Ocular Myasthenia Gravis. JAMA Neurol. 2015 Oct;72(10):1170-1174.26258604
33. Strijbos E, Verschuuren JJGM, Kuks JBM. Serum Acetylcholine Receptor Antibodies Before the Clinical Onset of Myasthenia Gravis. J Neuromuscul Dis. 2018;5(2):261-264.29865092
34. Sanders DB, Burns TM, Cutter GR, et al. Does change in acetylcholine receptor antibody level correlate with clinical change in myasthenia gravis? Muscle Nerve. 2014 Apr;49(4):483-486.23835683
35. Cikes N, Momoi MY, Williams CL, et al. Striational autoantibodies: quantitative detection by enzyme immunoassay in myasthenia gravis, thymoma, and recipients of D-penicillamine or allogeneic bone marrow. Mayo Clin Proc. 1988 May;63(5):474-481.3283472
36. Romi F, Skeie GO, Gilhus NE, Aarli JA. Striational antibodies in myasthenia gravis: reactivity and possible clinical significance. Arch Neurol. 2005 Mar;62(3):442-446.15767509
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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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