Ordering Recommendation

Secondary diagnostic testing for patients with generalized or ocular myasthenia gravis and no detectable antibodies to acetylcholine receptor (AChR).


Quantitative Radioimmunoassay


Mon, Thu


2-8 days

New York DOH Approval Status
This test is New York DOH approved.
Specimen Required
Patient Preparation

One 4 mL Plain Red or Serum Separator Tube (SST).

Specimen Preparation

Separate from cells ASAP or within 2 hours of collection.  Transfer 2 mL of serum to an ARUP Standard Transport Tube. (Min: 0.5 mL)

Storage/Transport Temperature


Unacceptable Conditions

Grossly lipemic, icteric, or hemolyzed specimens.


After separation from cells: Ambient: 48 hours; Refrigerated: 2 weeks; Frozen: 1 month (avoid multiple freeze/thaw cycles)

Reference Interval
Negative 0.00-0.03 nmol/L
Positive 0.04 nmol/L or greater

Interpretive Data

Muscle-specific kinase (MuSK) antibody is found in a subset of patients with myasthenia gravis, primarily those seronegative for muscle acetylcholine receptor (AChR) antibody. Decreasing antibody levels may be associated with therapeutic response; therefore, clinical correlation must be strongly considered. A negative test result does not rule out a diagnosis of myasthenia gravis.

Compliance Statement A: For laboratory developed tests using a manufacturer labeled ASR as the reagent providing the specificity of the assay. Analyte Specific Reagent. This test was developed and its performance characteristics determined by ARUP Laboratories. The U. S. Food and Drug Administration has not approved or cleared this test; however, the FDA has determined that such clearance or approval is not necessary.

Hotline History
CPT Codes


Component Test Code* Component Chart Name LOINC
3001577 Muscle-Specific Kinase (MuSK) Ab, IgG 51716-9
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.
  • Muscle-Specific Kinase Antibody by RIA
  • Muscle-Specific Receptor Tyrosine Kinase
  • MuSK
  • MuSK Autoantibody
Muscle-Specific Kinase (MuSK) Antibody, IgG