From the Guidelines
In type 1 diabetes, the antibodies that can be tested for include autoantibodies to insulin, glutamic acid decarboxylase (GAD), islet antigen 2 (IA-2), and zinc transporter 8 (ZnT8) 1. These autoantibodies are used for screening for presymptomatic type 1 diabetes and are particularly useful in individuals with a family history of type 1 diabetes or those with known elevated genetic risk. The main antibodies that can be tested for diagnostic purposes include:
- Glutamic acid decarboxylase antibodies (GADA or anti-GAD65)
- Islet cell antibodies (ICA)
- Insulin autoantibodies (IAA)
- Insulinoma-associated-2 autoantibodies (IA-2A)
- Zinc transporter 8 antibodies (ZnT8A) Testing for these antibodies is particularly useful for confirming type 1 diabetes diagnosis, especially in cases where the clinical presentation is unclear, as stated in the guidelines for laboratory analysis in the diagnosis and management of diabetes mellitus 1. The presence of multiple antibodies indicates a higher risk of developing type 1 diabetes in at-risk individuals, and standardized islet autoantibody tests are recommended for classification of diabetes in adults with phenotypic risk factors that overlap with those for type 1 diabetes 1. It is essential to measure islet autoantibodies in an accredited laboratory with an established quality control program and participation in a proficiency testing program, as emphasized in the guidelines for laboratory analysis in the diagnosis and management of diabetes mellitus 1. Overall, testing for these autoantibodies can help distinguish type 1 from type 2 diabetes, which is crucial for determining appropriate treatment and improving patient outcomes.
From the Research
Antibodies in Type 1 Diabetes
The following antibodies can be tested for in type 1 diabetes:
- Islet cell cytoplasmic autoantibodies (ICA) 2, 3, 4
- Insulin autoantibodies (IAA) 2, 5, 3, 6, 4
- Glutamic acid decarboxylase autoantibodies (GADA) 2, 5, 3, 6, 4
- Insulinoma associated-2 autoantibodies (IA-2A) 2, 5, 3, 6, 4
- Zinc transporter-8 autoantibodies (ZnT8A) 2, 5, 6
Clinical Significance of Antibodies
These antibodies can help diagnose type 1 diabetes and predict its development 2, 5, 3. They can also distinguish between type 1 and type 2 diabetes, especially in cases where the clinical presentation is unclear 2, 4. Additionally, the presence of these antibodies can indicate an increased risk of developing insulin dependency in patients initially diagnosed with type 2 diabetes 3, 4.
Methods for Detecting Antibodies
Various commercial assays are available for detecting these antibodies, including chemiluminescence immunoassays and immunoenzymatic assays 6. The agreement among these methods can vary, with the highest agreement found for anti-GAD antibodies and the lowest agreement for IAA 6.