GAD-65 autoantibody

Alphabetical Test listing

GAD-65 autoantibody-13403

GAD-65 autoantibody
Glutamic acid decarboxylase (GAD) autoantibody

This test is intended for the semi-quantitative determination of glutamic acid decarboxylase (GAD) antibody in human serum,it is useful as an aid in the diagnosis of type 1 diabetes mellitus (autoimmune mediated diabetes).


This test may exhibit interference when sample is collected from a person who is consuming a supplement with a high dose of biotin (also termed as vitamin B7 or B8, vitamin H, or coenzyme R).

It is recommended to ask all patients who may be indicated for this test about biotin supplementation. Patients should be cautioned to stop biotin consumption at least 72 hours prior to the collection of a sample.

0.5 mL
0.4 mL
Submission of the minimum volume does not allow for repeat testing

Immediately following collection, thoroughly mix sample by gently inverting 5 times

  1. Allow sample to clot for a minimum of 30 minutes
  2. Spin within two (2) hours of sample collection

Gold serum separator (SST) tube

  1. Allow sample to clot
  2. Spin within two (2) hours of sample collection
  3. Transfer serum to a Transfer vial/tube with cap - 12mL (LabCorp), labelled as serum

Ambient (preferred) - 14 days

Refrigerated - 14 days

Frozen - 14 days

Freeze/thaw cycles - stable x 3

  • Hemolysis
  • Gross lipemia
  • Non-serum sample
LabCorp Burlington (143008): R-LC
Mo - Fr
2 - 6 days

Enzyme linked immunosorbant assay (ELISA)


0.0 - 5.0 units/mL


This test allows for the detection of the presence of antibodies to glutamic acid decarboxylase, which provides early evidence of autoimmune disease activity; its measurement has been shown to be useful in assisting the physician in the prediction, diagnosis, and management of patients with diabetes.

Glutamic acid decarboxylase (GAD65) is an enzyme that is produced primarily by pancreatic islet cells. A number of recent studies indicate that patients with insulin-dependent diabetes mellitus (IDDM) often have antibodies to GAD65 and several other islet cell antigens. This is consistent with the hypothesis that IDDM is an autoimmune disease and that autoantibody production is an early step in the development of IDDM. Autoantibodies can be detected in many cases prior to the onset of glucose intolerance. The presence of GAD65 autoantibodies can be detected in many cases prior to the onset of glucose intolerance. The presence of GAD65 autoantibodies has been shown to be a strong predictive marker for the eventual onset of IDDM. Measurement of GAD65 antibody can also be of use in distinguishing insulin-dependent from non-insulin-dependent diabetics when the clinical history is ambiguous. GAD65 autoantibodies are often markedly elevated in patients with the stiff-person syndrome (also referred to as stiff-man syndrome), a condition that is associated with fluctuating stiffness and paroxysmal spasms of the trunk and legs.

Biotin supplement interference - see patient preparation
Result 56540-8