GAD65 Ab Assay (Sendout)

General Information

Lab Name

GAD65 Ab Assay

Lab Code

RGD65

Epic Name

GAD65 Antibody Assay (Sendout)

External Test Id

GD65S

Description

Useful For:

• Assessing susceptibility to autoimmune (type 1, insulin-dependent) diabetes mellitus and related endocrine disorders (e.g., thyroiditis and pernicious anemia)
• Distinguishing between patients with type 1 and type 2 diabetes

Ordering Guidance: Although a high positive result (>250 IU/mL) could be consistent with stiff-person syndrome, such a result by this assay has been shown to be insufficiently specific for this diagnosis¹ and is not recommended. For a comprehensive evaluation of patients with suspected stiff-person syndrome (classical or focal forms, such as stiff-limb or stiff-trunk) and progressive encephalomyelitis with rigidity and myoclonus, consider ordering Stiff-Person Spectrum Disorders Evaluation, Serum (Sendout) [OLTG #1108].

***Alert: Effective 10/13/26, this test is no longer available at Mayo as a standalone order. Samples will be forwarded to ARUP Laboratories for GAD65 Antibody (Sendout) [OLTG #1201] and results will be reported under Miscellaneous ARUP Frozen Test (Sendout) [RARUPZ] due to a change in methodology, units, and reference range. A new battery for the ARUP GAD65 Antibody test will be available on 12/01/2026.***

References

1. McKeon et al. GAD65 Antibody ELISA with Extended Reportable Range: Validation and Guidance for Neurological Practice. Annals of Clinical and Translational Neurology, 2026; 0:1–10. https://doi.org/10.1002/acn3.70378

Synonyms

64K Antibody, Anti GAD Ab, Anti-Glutamic Acid Decarboxylase Ab, Ataxia, Beta Cell Antibody, GD65S, Islet Cell Antibody, Pancreatic Islet Cell Ab

Components

Code	Name
RGAD65	GAD65 Antibody Assay