A Glutamic Acid Decarboxylase Autoantibodies test (GAD antibodies test) is used to help discover whether someone has either type 1 diabetes or Latent Autoimmune Diabetes of Adulthood ( LADA ).

A GAD antibody test may be favoured as a way of testing for which type of diabetes over a c-peptide test, which measures how much insulin is being produced by the body.

What is a GAD antibodies test?

A GAD test is a blood test which measures whether the body is producing a type of antibody which destroys its own GAD cells.

In type 1 diabetes , a number of autoantibodies are thought to circulate including those which target glutamic acid decarboxylase.

Presence of these autoantibodies suggests type 1 diabetes.

Why is a GAD test performed?

The test is performed to help determine which type of diabetes someone has.

The test is particularly useful for adults over 30 who get diabetes where a type 2 diabetes diagnosis is in doubt – such as if the patient is not overweight.

The test may also be used to determine whether gestational diabetes ( diabetes within pregnancy ) may be type 1 diabetes. The test can also be used to measure the progression of type 1 diabetes or indicate a risk of type 1 diabetes or LADA.

How is a GAD Autoantibody test done?

To carry out the test a blood sample is taken from the patient’s arm.

The test should be done before insulin therapy is started. The blood sample will need to be sent to be analysed by a lab before results can be obtained.

What will the GAD test results show?

Presence of the GAD antibodies is observed in 75% of people with type 1 diabetes at diagnosis.

If the test shows GAD antibodies are present, this indicates that the patient has type 1 diabetes. If no GAD antibodies are present, however, the test cannot be conclusive in saying that the patient does not have type 1 diabetes.

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