Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1036 page)

Decreased In

   Iron deficiency anemia (usually <10% in established deficiency)

   Anemias of infection and chronic diseases (e.g., uremia, RA, some neoplasms)

   Malignancy of the stomach and small intestine

ISLET AUTOANTIBODIES (IAA)

   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

*Recommended because it is most persistent islet autoantibody after onset of autoimmune DM.

   Limitations