Sign in →

Test ID GD65C Glutamic Acid Decarboxylase (GAD65) Antibody Assay, Spinal Fluid


Ordering Guidance


This test should not be requested in patients who have recently received radioisotopes, therapeutically or diagnostically, because of potential assay interference. The specific waiting period before specimen collection will depend on the isotope administered, the dose given, and the clearance rate in the individual patient. Specimens will be screened for radioactivity prior to analysis. Radioactive specimens received in the laboratory will be held one week and assayed if sufficiently decayed or canceled if radioactivity remains.



Specimen Required


Container/Tube: Sterile vial

Specimen Volume: 1.5 mL

Collection Instructions: Submit specimen from collection vial 2.


Forms

If not ordering electronically, complete, print, and send a Neurology Specialty Testing Client Test Request (T732) with the specimen.

Secondary ID

84221

Useful For

Possible use in evaluating patients with autoimmune encephalitis, stiff-person syndrome, autoimmune ataxia, autoimmune epilepsy, and other acquired central nervous system disorders affecting gabaminergic neurotransmission

Method Name

Radioimmunoassay (RIA)

Reporting Name

GAD65 Ab Assay, CSF

Specimen Type

CSF

Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time
CSF Refrigerated (preferred) 28 days
  Frozen  28 days
  Ambient  72 hours

Clinical Information

Glutamic acid decarboxylase (GAD) is a neuronal enzyme involved in the synthesis of the neurotransmitter gamma-aminobutyric acid (GABA). Serum antibodies directed against the 65-kDa isoform of GAD (GAD65) are detected in heightened frequency in a variety of autoimmune neurologic disorders, including autoimmune encephalitis, stiff-person (Moersch-Woltman) syndrome, autoimmune ataxia, and autoimmune epilepsy.

Reference Values

≤0.02 nmol/L

Reference values apply to all ages.

Cautions

Clinical utility of this test remains to be determined.

Day(s) Performed

Monday through Sunday

Report Available

3 to 6 days

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information

86341

NY State Approved

Yes