Anti-GAD ELISA Kit

Sample

Serum

Species Reactivity

Human

Detection Method

sELISA

Intended Use

Enzyme immunoassay for the determination of autoantibodies to Glutamic Acid Decarboxylase (GAD₆₅) in human serum.

Storage

Upon receipt, all test components must be stored at 2 °C to 8 °C, preferably in the original kit box. If stored properly in their original containers, all components are stable until their expiry date

Detection Range

Reliable accuracy, trueness, precision, linearity and recovery of test results have been observed within the measurement range of the assay from the LoQ to the upper calibrator in comprehensive studies. Samples with test results above the upper calibrator should be reported as >max. Samples with test results below the LoQ should be reported as ＜ min. If test results above the upper calibrator are observed, the samples may be tested at a higher dilution. The resulting antibody activity must be multiplied with the additional dilution factor.

Detection Limit

Limit of Blank (LoB) < 0.5 IU/mL
Limit of Quantitation (LoQ) < 1.0 IU/mL

Sensitivity

Sensitivity: 90.5 %
Specificity: 94.7 %

General Description

Type 1 diabetes, also known as insulin-dependent diabetes mellitus (IDDM), results from a chronic autoimmune destruction of the insulinsecreting pancreatic beta cells, probably initiated by exposure of genetically susceptible host to environmental agents. Autoimmune destruction of beta cells is thought to be completely asymptomatic until 80-90% of the cells are lost. This process may take years to complete and may occur at any time in all ages.
During the preclinical phase, this autoimmune process is marked by circulating autoantibodies to beta cell antigens. These autoantibodies, such as anti-insulin (IAA), anti-glutamic acid decarboxylase (GAD) and antityrosine phosphatase ICA 512 (IA2), are present years before the onset of type 1 diabetes and prior to clinical symptoms.
GAD, the enzyme that catalyzes the conversion of glutamate to GABA, has been identified in two isoforms, molecular weight 65.000 (GAD₆₅) and 67.000 (GAD₆₇). Although GAD autoantibodies are found in type 1 diabetes and in the rare neurological disorder Stiff-man syndrome (SMS), the GAD autoantibodies profile in the two diseases differs.
Autoantibodies of SMS patients recognize a combination of linear and conformational epitopes of GAD while GAD₆₅ autoantibodies in patients with type 1 diabetes are predominantly directed to the conformational epitopes. GAD₆₅ autoantibodies (GAD₆₅ Abs) are present in 70-80% of newly diagnosed patients with type 1 diabetes.
The combination of the autoantibodies to GAD₆₅ and IA2 is highly relevant for risk assessment of type 1 diabetes in children and adolescence. These tests in combination are more sensitive and predictive than ICA in risk groups, e.g. relatives of patients with type 1 diabetes.
GAD₆₅ Abs also occur in a subset of adults with type 2 diabetes. These patients can have pronounced hyperglycemia, and after therapy with oral hypoglycemic agents for several months to years they may become insulin dependent. Therefore, these patients are thought to have a slowly progressive form of type 1 diabetes, often called latent diabetes or latent autoimmune diabetes in adults (LADA).
The presence of GAD₆₅ Abs in sera of such patients is a sensitive and specific marker for future insulin dependency.