In patients who have not yet been treated with insulin but have symptoms suggestive of diabetes or a genetic predisposition based on family history, this test can be used to 1) distinguish among type 1 diabetes mellitus (autoimmune), type 2 diabetes mellitus, and atypical forms of diabetes, such as latent autoimmune diabetes in adults (LADA); or 2) to evaluate risk of future type 1 diabetes. This test may also be useful when evaluating patients for very rare autoimmune hypoglycemic syndrome.
In patients who have already been treated with insulin, insulin autoantibodies are usually of no clinical significance. Therefore, insulin antibody testing is generally not indicated for these patients. However, in rare cases, patients with suspected type 2 diabetes who have failed hypoglycemic treatment are tested and subsequently diagnosed with type 1 diabetes. This test is generally used along with other diabetes-related autoantibody tests such as GAD-65 Antibody (test code 34878) and IA-2 Antibody (test code 36177); all 3 antibodies can be ordered together as test code 10584. ZnT8 Antibody (test code 93022) may also be a useful additional test.
Testing for multiple diabetes-related antibodies may be helpful in diagnosis, because some forms of type 2 diabetes may initially resemble type 1 or have a positive result on testing for one of these autoantibodies. The higher the number of autoantibodies that are positive, the higher the likelihood of an autoimmune cause (type 1 or LADA) for diabetes mellitus.
For patients who do not yet have clinically apparent diabetes, a higher number of positive autoantibody tests predicts a higher risk of developing type 1 diabetes in the future. Rarely, insulin antibodies can take on a shape that resembles insulin closely enough to stimulate the insulin receptor, leading to hypoglycemia. The presence of insulin antibody in a hypoglycemic patient who has not previously been treated with insulin is suggestive of, but not definitive for, this rare syndrome.
Test results should be interpreted in the context of pertinent clinical and family history and physical examination findings.