MuSK Antibody Test
Label Mnemonic: MUSK
Epic Lab Code: LAB4827
Downtime Form: A-1a Miscellaneous Request
Commercial Mail-out Laboratory
5231 RCP
356-8593
Specimen(s):
Serum
Specimen Instructions:
Note: Collection date is required.
Collection Medium:
Red top tube 5 mL (Clot Activator)
Minimum:
Preferred Minimum: 2 mL serum in a red top tube.
Absolute Minimum: 0.5 mL serum in a red top tube.
Testing Schedule:
Test performed on Tuesday and Thursday.
Turn Around Time:
3 days upon receipt at reference laboratory
Reference Range:
< or =0.02 nmol/L
Interpretive Data:
A positive result, in the appropriate clinical context, confirms the diagnosis of autoimmune muscle-specific kinase myasthenia gravis.

Seropositivity justifies consideration of immunotherapy.
Comments:
This mailout test requires Neurology attending approval. Mailouts staff will not process order without approval. If approval is given, the name of the Neurology attending can be selected in the drop-down menu to the right of the approval warning in Epic when ordering the test.

This mailout test requires pathologist approval for orders during inpatient encounters. Mailouts staff will not process order without approval. The pathologist covering mailouts approval can be reached at pager #5379. If approval is given, the name of the pathologist can be selected in the drop-down menu to the right of the approval warning in Epic when ordering the test.

Useful For:
Diagnosis of autoimmune muscle-specific kinase (MuSK) myasthenia gravis.

Second-order test to aid in the diagnosis of autoimmune myasthenia gravis when first-line serologic tests are negative.

Establishing a quantitative baseline value for MuSK antibodies that allows comparison with future levels if weakness is worsening.

Cautions:
Immunosuppressant therapy is a common cause of false-seronegativity. It is, therefore, important to perform a comprehensive serological evaluation before initiating immunosuppressant therapy.

Interpretation of a patient's serological and clinical status is further complicated when characteristic signs of myasthenia gravis are obscured by a superimposed steroid-induced myopathy.
Methodology:
Radioimmunoassay (RIA)
CPT Code:
83519