- Last Update On : 2013-02-24
Glutamic acid decarboxylase (GAD) is present in highest concentration in brain and pancreatic beta cells. Antibodies specific for the 65 kDa isoform of glutamic acid decarboxylase (GAD65) comprise the majority of pancreatic islet cell autoantibodies. They appear years before the onset of clinical diabetes. Individuals with autoantibodies to GAD65 are at greater risk of developing type1diabetes than individuals without these antibodies. This test is useful in assessing susceptibility to type 1 diabetes mellitus, distinguishing between type 1 and type 2 diabetes mellitus, and confirming the diagnosis of stiff-man syndrome.
Anti-GAD65 autoantibodies are detectable in the sera of 76% of patients at the time of diagnosis of type 1 diabetes mellitus. They are also present in 93% of patients with the rare autoimmune disorder, stiff-man syndrome. Patients with type 1 diabetes mellitus usually have antibody levels between 0.03 and 20 nmol/L. High levels >20 nmol/L are usually found in patients with stiff-man syndrome and related autoimmune neurologic disorders such as acquired cerebellar ataxia.Approximately 20% of patients with other autoimmune neuromuscular disorders, such as myasthenia gravis and Lambert-Eaton myasthenic syndrome, have low titer antibody.
Specimen requirement is one red top or SST tube of blood.
Reference Range is <0.02 nmol/L.