Our three and a half year old daughter was diagnosed with type 1 diabetes in April 2003. Recently, our six year old son was displaying some initial symptoms, including wetting the bed twice and stomach aches after eating, so I did some random blood glucose checks. He has been 200 mg/dl [11.1 mmol.L] during the two hour post meal time, 145 mg/dl [8.1 mmol/L] and 168 mg/dl [9.3 mmol/L] during the middle of the night, although “normal” by morning.

To determine what was going on, we had autoantibody testing done on both of our sons. Our symptomatic son’s results were: IAA 0.001; GAA 0.017; ICA512 0.001. Our other son’s results were IAA0.001; GAA 0.023; ICA512 0.007. Our nurse explained that our symptomatic son’s GAA was “normal, ” but should have been negative and that it could be a red flag that he is headed down the path to type 1 diabetes. Could you assess these numbers and explain what they mean? Can you give me a percentage chance for developing diabetes? Can you determine that from the test results we have provided? Why is my other son’s positive GAA not considered a “red flag?” What are these particular autoantibodies and do they all have to be positive to develop diabetes?

I don’t understand any of these antibody results. You should ask these questions directly to your diabetes team since they will know where the antibodies are run and how to interpret them, what risks can be assigned, etc. In terms of the child who has intermittent hyperglycemia, unfortunately this is some risk for future development of diabetes and it depends how often and how high are the blood glucose readings. It is especially important to monitor him during episodes of any illness and with growth spurts, as well as with unusual symptoms so that he does not get dehydrated or severely ill.

SB
Additional comments from Dr. David Schwartz:

It would be even more helpful to me to interpret the antibody results if you gave the units of measurement and the name of the laboratory which ran them. Based on the numbers, I suspect these were an “index value”. In the reference laboratory with which I am familiar, the “normal index range” for GAD65 is 0-0.085; for IAA it’s 0-0.01; and for ICA512 it is 0-0.017. Without access to this information, I’d suspect that these antibody levels are not too exciting.

In general terms, a first degree relative (sibling, parent, child) of someone with type 1 diabetes has about a 5 percent chance of developing type one diabetes also. That means 1 out of 20 first degree relatives. So, if your child who has type 1 diabetes would need about 16 more first degree relatives to find the “right one.” Of course, those are odds and do not reflect specifically on any individual’s likelihood of developing type 1 diabetes. If that first degree relative has positive antibodies, the risk increases 10 fold to about 50 percent. No better than flipping a coin, you say? Yes, but still a 10 fold increase. Would you go to Las Vegas knowing that you will likely win/lose 10 times more often?

The common antibody proteins tested for include antibodies to:

insulin itself (insulin autoantibody; IAA);

a protein within the insulin producing cell (islet cell) designated ICA 512 (“islet cell antibody number 512; also called IA2 or tyrosine kinase antibody);

a protein within the islet cell called GAD 65 (Glutamic Acid Decarboxylase number 65) [Now, aren’t you glad these are abbreviated?]

They do NOT ALL have to be positive to develop diabetes. In fact, NONE of them may be positive in type 1 diabetes (this has been called type 1b diabetes; see a previous Ask the Diabetes Team question), but at least one antibody is commonly present during classic type 1a diabetes.

As for screening your other children, the diagnosis of diabetes is determined by GLUCOSE measurements (by venipuncture), not A1c values or the presence of pancreatic antibodies. The risk of diabetes can be suspected based on antibody levels, but we have no preventative. You may have just caused your anxiety level to go up by doing these tests. You may have caused insurability to go down (or insurance premiums to go up).

DS