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Question:

From Indiana, USA:

About a month ago, you answered my questions concerning my now 11year old daughter who has ocular myasthenia gravis along with diabetes. At the time, all the test results were not in, and they were treating her as though she has type 2 diabetes with metformin with excellent results. However, her antibody panel is as follows GAD-2.9, islet cell-12, insulin antibody-3.7. Is this a true indicator of type 1 diabetes? We do not go back to see the endocrinologist for several months, and I have gotten limited information from the diabetes nurse. Now I am even more confused than I was before. Can you help me interpret this?

Answer:

I am sorry to say that I can't help you, but let me try to explain why. When you first wrote it seemed probable to me that since the ocular myasthenia gravis is known to be an autoimmune disorder that the diabetes was likely to have the same basis, despite the fact that the initial presentation may have suggested type 2 diabetes. The critical tests therefore were for the presence of antibodies, and it is here that the confusion lies.

Antibody testing for type 1A (autoimmune) diabetes is a relatively recent procedure for routine clinical laboratories, and, for many reasons, a variety of different methods are used which means that different laboratories will give different numerical results on the same sample just because they do the measurement differently. To get around these variations, the CDC (Communicable Disease Center) some months ago had a meeting in which it was decided that for a laboratory to be certified in this procedure they had to process at least 100 normals, and they then had to express the result as positive or negative with positive being equal to or greater than three standard deviations above the normal mean. (Your daughter's doctor can explain what this means in statistical terms.) The reason for this is that for the test to be predictive of or to confirm clinical diabetes you need to show not only that some antibody is present; but how abnormal the titer is. In your child's case, there are two alternatives.

One is to await events, and if she begins to need insulin then this is the honeymoon period and the diagnosis is almost certainly type 1A diabetes. If, on the other hand, she remains in good control on [metformin, then there are other possibilities including type 2 diabetes. The other, if you cannot get the necessary information from your doctor or the clinical laboratory director would be to repeat the tests, sending the sample to a commercial laboratory like Quest Diagnostics which does meet CDC criteria.

DOB

DTQ-20030915144945
Original posting 22 Sep 2003
Posted to Diagnosis and Symptoms

  
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Last Updated: Tuesday April 06, 2010 15:09:52
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