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Test Code GD65S Glutamic Acid Decarboxylase (GAD65) Antibody Assay, Serum

Reporting Name

GAD65 Ab Assay, S

Useful For

Assessing susceptibility to autoimmune (type 1, insulin-dependent) diabetes mellitus and related endocrine disorders (eg, thyroiditis and pernicious anemia)

 

Distinguishing between patients with type 1 and type 2 diabetes

 

Confirming a diagnosis of stiff-man syndrome, autoimmune encephalitis, autoimmune ataxia, brain stem encephalitis, autoimmune epilepsy, autoimmune myelopathy

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Serum


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 1 week and assayed if sufficiently decayed or canceled if radioactivity remains.



Specimen Required


Collection Container/Tube:

Preferred: Red top

Acceptable: Serum gel

Submission Container/Tube: Plastic vial

Specimen Volume: 1.5 mL

Collection Instructions: Centrifuge and aliquot serum into a plastic vial.


Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 28 days
  Frozen  28 days
  Ambient  72 hours

Reference Values

≤0.02 nmol/L

Reference values apply to all ages.

Day(s) Performed

Monday through Sunday

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

LOINC Code Information

Test ID Test Order Name Order LOINC Value
GD65S GAD65 Ab Assay, S 30347-9

 

Result ID Test Result Name Result LOINC Value
81596 GAD65 Ab Assay, S 30347-9

Method Description

(125)I-labeled recombinant human glutamic acid decarboxylase 65 (GAD65) is incubated with the patient sample. Anti-human IgG is then added to form an immunoprecipitate. After washing the immunoprecipitate, the amount of (125)I-labeled antigen in the immunoprecipitate is measured using a gamma-counter. The amount of gamma emission in the precipitate is proportional to the amount of GAD65-IgG in the sample. Results are reported as units of precipitated antigen (nMol) per L of patient sample.(Walikonis JE, Lennon VA. Radioimmunoassay for glutamic acid decarboxylase [GAD65] autoantibodies as a diagnostic aid for stiff-man syndrome and a correlate of susceptibility to type 1 diabetes mellitus. Mayo Clin Proc. 1998;73[12]:1161-1166; Horta ES, Lennon VA, Lachance DH, et al. Neural autoantibody clusters aid diagnosis of cancer. Clin Cancer Res. 2014;20[14]:3862-9386)

Report Available

3 to 6 days

Reject Due To

Gross hemolysis Reject
Gross lipemia Reject
Gross icterus Reject

Method Name

Radioimmunoassay (RIA)

Secondary ID

81596