DIAGNOSTIC TEST 089

GAD Antibodies

Diagnostic test for antibodies against GAD. For suspicion of type 1 diabetes (T1D) and Stiff Person Syndrome, Autoimmune Encephalitis, and epilepsy.

swedac

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Indication

Suspicion of type 1 diabetes (T1D) Antibodies against GAD may also be associated with neurological diseases like Stiff Person Syndrome, Limbic Encephalitis, epilepsy, and cerebellar ataxia.

Sample material

Serum

  • Minim. volume: 0,5 mL

CSF

  • Minim. volume: 2,0 mL

Transport

Within Sweden

  • room temperature

International

  • cold

Method

Serum

  • ELISA, Immunoblot and Indirect immunofluorescence (IIF)

CSF

  • Immunoblot and Indirect immunofluorescence (IIF)

According to guidelines Updated Diagnostic Criteria for Paraneoplastic Neurologic Syndromes, anti-neuronal antibodies should be detected by at least two independent methods to be reliable. At Wieslab IIF and immunoblot are used.

Reference interval

Serum

  • ELISA: <10 IU/mL negative
  • Immunoblot: <6 negative
  • Indirect Immunofluorescence: <1:10 negative

CSF

  • Immunoblot: negative
  • Indirect immunofluorescence: negative

Result

Serum

  • ELISA: results are reported as negative, borderline, or positive with a concentration (IU/mL).
  • Immunoblot: results are reported as negative, borderline, or positive with an intensity value.
  • Indirect immunofluorescence (IIF): results are reported as negative or positive. Positive results will be titrated.

CSF

  • Immunoblot: Results are reported as negative, borderline, or positive.
  • Indirect immunofluorescence (IIF): Results are reported as negative or positive.

Interpretation

There are two isoforms of GAD (65 kDa and 67 kDa). GAD-65 is primarily expressed in pancreas while both GAD-65 and GAD-67 are expressed in the brain. In type 1 diabetes (T1D), antibodies against GAD-65 occur, while both specificities of antibodies can be seen in neurological conditions. Patients with neurological symptoms often have higher levels of anti-GAD antibodies compared to patients with T1D.

IgG-antibodies against GAD occur in serum in type 1 diabetes (T1D) and are detected in approximately 70-80% of the cases. The antibodies can often be detected prior to diagnosis. Simultaneous presence of antibodies against islet cells, ß-cell antigen 2 (IA-2), insulin (IAA), and zinc transporter 8, strongly indicate manifestation or future development of T1D.

A slight increase of anti-GAD antibodies can be present during other autoimmune endocrine diseases, especially autoimmune thyroiditis.

Anti-GAD antibodies occur in 60% of patients with Stiff Person Syndrome and can then be detected in both serum and CSF. Anti-GAD antibodies may also be associated with limbic encephalitis, epilepsy, and cerebellar ataxia.

Antibodies against GAD-65 are graded as Lower-risk antibodies and give 0 points in the PNS score, according to Updated Diagnostic Criteria for Paraneoplastic Neurologic Syndromes, but has been reported in breast cancer, small cell lung cancer, and endocrine tumors.

References

  • Budhram A et al Journal of Neurology, Neurosurgery & Psychiatry. 2021. Clinical spectrum of high-titre GAD65 antibodies PMID: 33563803
  • Graus F et al. Neurol Neuroimmunol Neuroinflamm. 2021. Updated Diagnostic Criteria for Paraneoplastic Neurologic Syndromes. PMID: 34006622
  • Guasp M, Dalmau J. Neurology. 2023. Searching for Neuronal
  • Dalakas MC. Continuum (Minneap Minn). 2024. Stiff Person Syndrome and GAD Antibody-Spectrum Disorders. PMID: 39088290
  • Brown RL et al. J Neurol. 2025. GAD antibodies in neurological disease: a critical evaluation of the utility and treatment implications of GAD antibodies in clinical practice. PMID: 39985693
  • Rada A et al. Neurol Neuroimmunol Neuroinflamm. 2025. Temporal Lobe Epilepsy Associated With Glutamic Acid Decarboxylase Antibodies: Defining a Distinct Epilepsy Syndrome. PMID: 40505070

Included in these panels

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How to order

This test is available worldwide for hospitals, clinics, and physicians.

  1. Print and complete the request form

    Download the request form. Clearly state the name and phone number of the referring hospital, clinic, or physician. If you are a new customer, please also include a completed customer information form.

  2. Prepare your samples

    Serum: At least 0.5 mL serum (plain serum tubes without additives).
    CSF: At least 2 mL CSF (polypropylene tubes).

  3. Send samples and request form

    Within Sweden
    Samples can be sent at room temperature to:
    Envelopes and smaller boxes:
    Wieslab AB, Box 50117, 20211 Malmö, Sweden

    Larger boxes and frozen samples:
    Wieslab AB, Lundavägen 151, 21224 Malmö, Sweden

    International
    Send samples cold to:
    Wieslab AB, Lundavägen 151, 21224 Malmö, Sweden

Last updated: 2026-08-27