Glutamic Acid Decarboxylase (GAD65) Antibody Assay, Serum

GAD Antibody, GAD65, stiff-man syndrome

Test Codes

EPIC: LAB1232002, Beaker: GAD65, Quest: 34878

Department

Send Outs

Specimen Collection Criteria

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

Physician Office/Draw Specimen Preparation

Let specimen clot 30-60 minutes then centrifuge to separate serum from cells. Transfer serum to plastic transport tube and maintain at room temperature (20-26°C or 68-78.8°F) prior to transport.

Preparation for Courier Transport

Transport: 1.0 mL serum, room temperature (20-26°C or 68-78.8°F). (Minimum: 0.5 mL)

Rejection Criteria

• Grossly hemolyzed specimens.
• Grossly icteric specimens.
• Grossly lipemic specimens.
• Specimens not collected and processed as indicated.

In-Lab Processing

Let specimen clot 30-60 minutes then centrifuge to separate serum from cells. Transfer serum to plastic transport tube and maintain at room temperature (20-26°C or 68-78.8°F) prior to transport.

Transport: 1.0 mL serum, room temperature (20-26°C or 68-78.8°F). (Minimum: 0.5 mL)

 

Storage

Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): 7 days
Refrigerated (2-8°C or 36-46°F): 14 days
Frozen (-20°C/-4°F or below): 60 days

Specimen Storage in Department Prior to Disposal:

Specimen retention time is determined by the policy of the reference laboratory. Contact the Send Outs Laboratory with any questions.

Laboratory

Sent to Quest Diagnostics, Wood Dale, IL.

Performed

Sunday – Friday.
Results available in 3-5 days.

Reference Range

<5 IU/mL.

Test Methodology

Enzyme Linked Immunosorbent Assay (ELISA)

Clinical Utility

Glutamic Acid Decarboxylase-65 Antibody - Glutamic acid decarboxylase (GAD-65) antibody is useful to diagnose insulin dependent diabetes mellitus [Type I diabetes (autoimmune-mediated diabetes)] to assess risk for development of Type I diabetes, to predict onset of Type I diabetes, and risk of development of related endocrine disorders, e.g., thyroiditis. Before clinical onset, Type I diabetes is characterized by lymphocytic infiltration of the islet cells, and by circulating autoantibodies against a variety of islet cell antigens, including GAD-65, IA-2 (a tyrosine phosphatase-like protein), and insulin (IAA).

CPT Codes

86341
LOINC:  56540-8

Contacts

Last Updated

11/19/2025