Research

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Diabetic autoantibodies

(September 2007)

(Download  Diabetic Autoantibodies.pdf)

Which patients should be tested for diabetic autoantibodies?

Patients with newly diagnosed Diabetes Mellitus, both types 1 and 2, may benefit from autoantibody testing. The presence of autoantibodies is specific for Type 1 diabetes, and can precede the onset of clinically apparent diabetes. Patients with such autoantibodies should be considered at risk for diabetic ketoacidosis, and most will require insulin therapy. Classical Type 1 patients are young and thin, whereas classical Type 2 patients are not. This is not always the case, and Type 1 patients may initially be diagnosed as Type 2 (or vice versa). 12% of 4,545 patients in the UK Prospective Diabetes Study initially considered Type 2 were found to be antibody positive, and most (58%) required insulin before the end of the study. The Freemantle Diabetes Study showed 15% of patients of Aboriginal or Torres Island ethnicity, considered to have Type 2 diabetes, were positive for GAD autoantibodies.

Patients with:

Reason

  • Newley diagnosed Diabetes Mellitus
  • Ketosis risk assessment (as above)
  • Coeliac Disease
  • Autoimmune Thyroid Disease
  • Addison's Disease
  • B12 deficiency
  • Predict future risk of diabetes (may have an Autoimmune Polendocrine Syndrome)

What tests should I ask for?

HAPS is pleased to offer the following autoantibody testing for diabetes mellitus:

Abbreviation

Autoantibody name

Specificity

ICA

Islet cell antigen

97%

IA-2

Insulinoma Associated Antigen-2

99%

GAD

Glutamic Acid Decarboxylase (65kD)

94%

Presence of any of the above “diabetic antibodies” is highly suggestive of Type 1a (autoimmune, ketosis-prone) diabetes. Patients without any of the above three antibodies are unlikely to have Type 1a diabetes (88% sensitivity). HAPS recommend the use of all three antibody tests when assessing a patient’s risk.

Autoantibodies to insulin (IAA) can also be measured, but as such antibodies are relatively insensitive (particularly in adults), imprecise, and add little to sensitivity when the above three antibodies are used, HAPS is currently sending such requests off-site for analysis.

Is it free for the patient?

These assays are covered by the Medicare Benefits Schedule (Item 71109), for Medicare Eligible patients.

Requirements for collection?

Plain serum tube, 5mL. Transport at 4 degrees C.

Author

This information sheet was written by Dr Theo de Malmanche.

The Immunology Department of HAPS can be contacted by telephone (49214018) or facsimile (49214023).