Lab Test

Acetylcholine Receptor Modulating Antibody

Myasthenia Gravis (MG) , ARUP #99521, Antrim #80130, EPIC: LAB5923, SOFT: XARMO

Specimen Collection Criteria

Collect (preferred specimen): One Gold-top SST tube.
Also acceptable: One plain Red-top tube.

Physician Office/Drawsite Specimen Preparation

Let specimen clot 30-60 minutes then centrifuge to separate serum from cells within two hours of collection. Transfer serum to a plastic transport tube and refrigerate (2-8°C or 36-46°F).

Preparation for Courier Transport

Transport: 0.5 mL serum, refrigerated (2-8°C or 36-46°F). (Min: 0.3 mL)

Rejection Criteria

  • Hemolyzed specimens.
  • Severly lipemic specimens.
  • Specimens not collected and processed as indicated.


Ambient: 2 hours
Refrigerated: 7 days
Frozen: 1 month (avoid multiple freeze-thaw cycles)


Sunday - Friday.
Results available in 3-8 days.

Reference Range

Negative: 0-45% modulation.
Positive: 46% or greater modulation.

Test Methodology

Semi-Quantitative Flow Cytometry.


Approximately 85-90% of patients with myasthenia gravis (MG) express antibodies to the acetylcholine receptor (AChR), which can be divided into binding, blocking, and modulating antibody. Binding antibody can activate complement and lead to loss of AChR. Blocking antibody may impair AChR binding to the receptor, leading to poor muscle contraction. Modulating antibody causes receptor endocytosis resulting in loss of AChR expression, which correlates most closely with clinical severity of disease. Approximately 10-15% of individuals with confirmed myasthenia gravis have no measurable binding, blocking, or modulating antibody.

CPT Code


Test Codes

ARUP #99521, Antrim #80130, EPIC: LAB5923, SOFT: XARMO

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This directory currently reflects information only for specimens collected and/or processed at the
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