Anti–GAD65 Antibodies
Test details
Paraneoplastic neurological syndromes (PNS) are immune-mediated disorders that can affect any part of the nervous system, occur in association with cancer and are often supported by the presence of specific neuronal autoantibodies.
Neuronal autoantibodies are classified as high-, intermediate-, or low-risk for paraneoplastic aetiology. Cancer association is 30–70% for intermediate-risk antibodies and <30% for low-risk antibodies. In general, intermediate- and low-risk antibodies are pathogenic, and patients often respond well to immunosuppressive therapy.
Anti-GAD65 antibodies are markers of autoimmune neuronal diseases such as limbic encephalitis, stiff-person syndrome, and cerebellar ataxia. Their association with small-cell lung carcinoma (SCLC), neuroendocrine tumours, and thymoma is <15%.
Anti-GAD antibodies – particularly anti-GAD65 – are found in 80–90% of patients with type 1 diabetes and in 60–80% of patients with stiff-person syndrome, a disorder characterised by progressive stiffness and muscle spasms. However, anti-GAD antibodies are not present in all stiff-person syndrome patients and are not required for diagnosis. There is no clear correlation between anti-GAD antibody titre and disease severity.
Sample type
Serum, EDTA plasma, heparin plasma, citrate plasma, CSF
Method
Immunoblot, IFA cells
Preparation
Fasting for at least 8-12 hours before sampling
Storage conditions
Refer to the Health Service Charter to check storage conditions
Shipping
+2/+8°C
References
Baizabal-Carvallo JF, Jankovic J. Stiff-person syndrome: insights into a complex autoimmune disorder. J Neurol Neurosurg Psychiatry. 2015 Aug;86(8):840-8. doi: 10.1136/jnnp-2014-309201. Epub 2014 Dec 15. PMID: 25511790.
Baizabal-Carvallo JF. The neurological syndromes associated with glutamic acid decarboxylase antibodies. J Autoimmun. 2019 Jul;101:35-47. doi: 10.1016/j.jaut.2019.04.007. Epub 2019 Apr 15. PMID: 31000408.
Graus F, Vogrig A, Muñiz-Castrillo S, Antoine JG, Desestret V, Dubey D, Giometto B, Irani SR, Joubert B, Leypoldt F, McKeon A, Prüss H, Psimaras D, Thomas L, Titulaer MJ, Vedeler CA, Verschuuren JJ, Dalmau J, Honnorat J. Updated Diagnostic Criteria for Paraneoplastic Neurologic Syndromes. Neurol Neuroimmunol Neuroinflamm. 2021 May 18;8(4):e1014. doi: 10.1212/NXI.0000000000001014. PMID: 34006622; PMCID: PMC8237398.
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