May 11, 2011
Diagnosis and Symptoms
Question from Massachusetts:
My son was diagnosed with diabetes in the Fall of 2010. Initially, they diagnosed him as type 2, but his antibody testing came back positive for IAA and GAD-65. They changed his diagnosis to type 1.5 or “double diabetes.” At the time, his insulin level was 35.1, IAA was 5.2, and GAD-65 was 1.7. They started him on metformin, and he has been exercising and limiting carbohydrates. I took him in for follow-up recently because his postprandial numbers have been higher (160s to low 200s mg/dl [8.9 to 12 mmol/L]) and he has not been feeling well. More bloodwork was done, including repeat antibody levels. These results show an insulin level of 11.0, IAA < 2.0, and GAD-65 < 1.0. As I understand it, these results are "negative" for type 1 antibodies. Would these results indicate the "type 1.5" diagnosis is inaccurate or can this sometimes happen where antibody levels regress with treatment such as metformin but it still indicates an autoimmune type of diabetes?
Answer:
Antibody testing is not as specific as we would all like. Sometimes positive antibodies then become negative and sometimes the reverse. Sometimes they go up and down. It does not mean much of anything that is predictive. Metformin itself does not change the antibody levels so that is not the explanation. The positive antibodies predict that he will likely need insulin sooner rather than later and perhaps not always be able to get glucose control from just metformin, however, since they usually reflect more likelihood of losing some insulin production capability. Weight loss, exercise, and lowered glycemic index of food eaten are all key to successful treatment based upon frequent blood glucose monitoring results as a guide to when metformin doses need to be increased and even when insulin would be added. Stay in close contact with your treatment team for such guidance, of course.
SB
