Diabetes-related Autoantibodies

Islet cell cytoplasmic autoantibodies (ICA), insulin autoantibodies (IAA), glutamic acid decarboxylase antibodies (GADA), and insulinoma-associated-2 autoantibodies (IA-2A) are a group of tests that measure diabetes-related autoantibodies. These autoantibodies do not cause type 1 diabetes but serve as markers of the body’s destructive immune response against its own cells that produce insulin (e.g., the beta cells in the pancreas). When about 80-90% of the beta cells are destroyed by the immune system, symptoms of diabetes such as frequent urination, thirst, weight loss, and poor wound healing occur. Without sufficient insulin action, hyperglycemia results. If the symptoms are not detected and hyperglycemia is not treated, a diabetic medical crisis can occur that can develop over a few weeks or even a few days.

The ICA test measures a group of islet cell autoantibodies targeted against a variety of islet cell proteins. It is a semi-quantitative test performed by indirect immunofluorescence. GADA and IA-2A are antibodies against two of the specific islet cell antigens. The only antigen believed to be highly specific to beta cells is insulin, and antibodies to insulin are abbreviated IAA. The IAA test does not differentiate whether the body’s immune system is making autoantibodies against insulin or if the immune system is making antibodies against insulin that has been injected (either human or animal) in the treatment of any type of diabetes.

About 10% of all cases of diabetes are type 1 (autoimmune) in origin. Of these, about 75% are diagnosed in patients younger than 20 years old. Type 1 diabetes was previously known as juvenile or insulin-dependent diabetes but has been re-characterized to reflect beta cell destruction. Islet autoantibodies can be detected in the blood stream months to years before the development of type 1 diabetes. While nondiabetic individuals with islet autoantibodies are at high risk for the development of type 1 diabetes, not every person with islet autoantibodies will develop type 1 diabetes. When autoimmune type 1 diabetes is present, one or more of the diabetes autoantibodies will be present in about 95% of patients at the time of initial diagnosis. Testing nondiabetic individuals for islet autoantibodies is recommended only as part of a research study.

A blood sample is obtained by inserting a needle into a vein in the arm.