Islet Autoantibodies (IAA)

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Subject: Islet Autoantibodies (IAA)

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Definition

  • Diabetes-related (islet) autoantibody testing is primarily ordered to help distinguish between autoimmune type 1 DM and DM due to other causes (e.g., diabetes resulting from obesity and insulin resistance). In conjunction with family history, HLA typing, and measurement of other islet cell autoantibodies, insulin autoantibody measurements are useful in predicting the future development of type 1 DM in asymptomatic children, adolescent, and young adults. If IAA, glutamic acid decarboxylase autoantibodies, or insulinoma-2–associated autoantibodies are present in an individual with DM, the diagnosis of type 1 DM has been established.

  • Normal range: negative.

Use

  • Differential diagnosis of type 1 versus type 2 DM.

  • Evaluating diabetics with insulin resistance.

  • Investigation of hypoglycemia in nondiabetic subjects.

  • Marker for type 1 DM. In 95% of cases of new-onset type 1 DM, ≤1 of 4 is positive (see Table 16.51).

 
TABLE 16–51
Autoimmune Antibodies in Type 1 DM

Limitations

  • IAA testing must be performed before insulin therapy is initiated.

  • Children at onset of type 1 DM are more commonly IAA positive than adults. Up to 80% of new–onset type 1 DM patients before the age of 5 years have IAA compared with only approximately 30% for adults.

 
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