Pathology Handbook

GAD antibodies


Glutamic Acid Dehydrogenase antibodies

Clinical Indications

Type I autoimmune diabetes mellitus (IDDM) Latent autoimmune diabetes in adults (LADA) First degree relatives of patients with Type I diabetes Stiff Person Syndrome (SPS) Please note: Anti GAD antibodies are found in 65 - 85% of patients with Type I Diabetes, in 70 - 90% of patients with LADA, approximately 80% of healthy relatives of patients with Type I Diabetes and a small percentage of patients with Type II Diabetes. Levels are generally low in Diabetes (<100 U/mL). Anti GAD antibodies are found in approximately 60% of patients with Stiff Person Syndrome. Levels are generally high in SPS (>300 U/mL).

Test Includes

Detection of IgG antibodies to Glutamic acid Dehydrogenase.

Request Form 

Request via ICE


Assay is performed weekly.

Specific Criteria

It is essential to provide relevant clinical information.

Patient Preparation

No special preparation is required.

Turnaround Time

All samples are generally sent to referral laboratory within 3 working days of receipt in the laboratory. Samples are batched and the assay is performed once per week.


Serum in red top tube

Gold top (SST) tube will be accepted


7 ml


Vacutainer red top


Samples should be transported to the laboratory as soon as is practicably possible.

Causes for Rejection

Unlabelled/inadequately labelled sample

Inadequately completed request form

Delay in sample reaching laboratory.

Laboratory Handling 

Aliquot and store at 4-8°C prior to testing and at -20°C or below for up to 1 month after receipt.

Reference Range

Results shoulf be interpreted as follows

Negative result is 0-5.0 U/ml

Equivocal result is 5.1-25.0 U/ml

Positive result is >25.0 U/ml