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Question:

From Florida, USA:

Our 7 year-old son was diagnosed 15 months ago with Type 1 diabetes. For almost a full year, his maximum insulin intake was 3 units a day. A month ago, it jumped to 10 units a day. Three months ago, he had an Islet Cell Antibody (ICA) test performed. The results came back negative, indicating that no autoantibodies were present in his blood. According to your glossary entry for ICA's, the common antibodies routinely assayed are IAA, GAD65, ICA512, EMA, and Anti 21-hydroxylase. Given that this test came back negative, we can assume that none of these 5 common antibodies are present in our son. What additional antibodies or other active agents could cause type 1 diabetes? Are there any tests available to positively indicate which one is causing his condition?

Answer:

In response to your questions, please note: the term Islet Cell Antibodies, or ICA, refers to a variety of antibodies reacting against several molecules within the pancreatic islets, including GAD65, IA-2 or ICA512, insulin, and a few others. The ICA test is now an old test that only tells whether one's blood contains antibodies against one or more of the above molecules. However, it does not say exactly which antibody or antibodies are present. Moreover, a negative ICA test does not formally exclude that one may have antibodies to one of the above molecules. Specific tests to measure antibodies against each one of the above mentioned molecules are available to answer your question.

In time, however, antibodies tend to disappear in most patients. Chances are that your son would test negative for all (excluding insulin antibodies [IAA] since their levels can be stimulated by insulin therapy and thus the IAA test is not very useful to answer your question now). Also note that the presence or absence of antibodies to GAD65 or IA-2 would not make much difference for your son's diabetes at this stage. The antibodies simply mark the occurrence of an autoimmune attack against the insulin-producing cells in the pancreatic islets. Once most or all insulin-producing cells are destroyed, diabetes symptoms develop. Unfortunately, the damage to the insulin-producing cells is irreversible, and diabetes will not go away even if antibodies do. Thus, measuring any type of ICA at this stage would not be very useful.

Anti-21 hydroxylase and EMA antibodies are not specific for pancreatic islets and diabetes, and you get no information on them by having an ICA test done. The Anti-21 hydroxylase antibody test is a predictor of Addison's disease, an autoimmune disease of the adrenal gland occurring in 1/200 to 1/1,000 individuals with Type 1 diabetes. The EMA test is a predictor of Celiac Disease, an autoimmune disorder affecting the gut that can be treated with gluten-free diet. Anti-21 hydroxylase and EMA antibodies should be measured periodically, and would be more useful for your son to have these tests done rather then the ICA. The Barbara Davis Center for Childhood Diabetes in Denver, Colorado, offers both tests, as well as the complete battery of antibody tests for GAD65, ICA512, and insulin. You can find more information about these tests at the Barbara Davis Center web site.

Alberto Pugliese, M.D.
Diabetes Research Institute
University of Miami School of Medicine

Original posting 9 Oct 1998
Posted to Diagnosis and Symptoms

  
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Last Updated: Tuesday April 06, 2010 15:09:02
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