3802 – Medizym® anti-GAD
The Medizym® anti-GAD is a quantitative immunoassay for the determination of antibodies against Glutamic Acid Decarboxylase (GAD65) in human serum. The Medizym® anti-GAD is intended as an aid in the diagnosis of diabetes mellitus type I in conjunction with other clinical and laboratory findings.
Genetic susceptibility and exposure to environmental factors are probable causes of type 1 diabetes, alternatively referred to as insulin-dependent diabetes mellitus (IDDM), a chronic autoimmune destruction of the insulin-secreting pancreatic beta cells. This condition is believed to be completely asymptomatic until about 80-90% of the cells are destroyed, a process that may take years to complete, occurring regardless of age.
Circulating autoantibodies to beta cell antigens are characteristic of the preclinical phase of the autoimmune process. These autoantibodies, especially anti-glutamic acid decarboxylase (GAD), anti-insulin (IAA), and anti-tyrosine phosphatase ICA 512 (IA2), are present several years prior to appearance of clinical symptoms. Autoantibodies to GAD, the enzyme that catalyses glutamate to gamma-Aminobutyric acid (GABA), with two isoforms, GAD65 (65 kDa molecular weight) and GAD67 (67 kDa molecular weight), are found in type 1 diabetes and in Stiff-man syndrome (SMS), a rare neurological disorder. The GAD autoantibodies profile in the two diseases differs in their preference to the conformational epitopes, wherein GAD65 autoantibodies are present in 70-80% of newly diagnosed patients with type 1 diabetes.
An essential part of the risk assessment of type 1 diabetes in children and adolescent includes a combination of the autoantibodies to GAD65 and IA2, offering a more sensitive and predictive method than ICA in risk groups, e.g. relatives of type 1 diabetes patients. GAD65 is also important in the diagnosis of type 2 diabetes adults with pronounced hyperglycemia where the patients become insulin dependent several months to years after therapy with oral hypoglycemic agents. Such patients are thought to have latent autoimmune diabetes in adults, a slowly progressive form of type 1 diabetes. GAD65 detection in this kind of patients provides a sensitive and specific diagnostic evidence for future dependence on insulin.
The ELISA (Enzyme Linked Immunosorbent Assay) is an immunoassay for the determination of specific antibodies. The strips of the microtiter plate are coated with test-specific antigens. If antibodies are present in the patient´s sample, they bind to the antigens. A second biotinylated antigen recognizes to the fixed antibody. The assay utilizes the ability of antibodies to act bivalently with immobilized and soluble antigens. Streptavidin conjugated with the enzyme peroxidase detects the generated immune complex. A colorless substrate is converted into the colored product. The signal intensity of the reaction product is proportional to the antibody activity in the sample. After stopping the signal intensity of the reaction product is measured photometrically.
The immunoassay is designed for manual professional in vitro diagnostic use.
|Indication||Diabetes mellitus Type 1|
|Description||Enzyme immunoassay for the quantitative determination of antibodies against Glutamic Acid Decarboxylase (GAD65) in human serum|
|Format||Microtiter plate coated with recombinant human GAD65|
|Total incubation time||160 min.|
|Sample volume||25 µL serum|
|No. of determinations||96 (89 x 1) + 5 x Calibrators + 2 x Controls|