< Return to all Tests

Test Category: Immunology

Investigation Name:Glutamic acid decarboxylase (GAD) antibody

Alias or Abbreviation:GAD

Intro:

Indication: Type 1 Diabetes; Stiff Person Syndrome Further information: Glutamic acid decarboxylase (GAD) exists as two different isoforms, GAD65 and GAD67. GAD antibodies directed against linear epitopes are associated with Stiff Persons Syndrome (GAD65 and GAD67) whilst those recognising conformational epitopes are seen in insulin dependent diabetes (GAD65). Antibodies to GAD65 and GAD67 are cross reactive. GAD65 antibodies are associated with autoimmune diabetes in the prediabetic stage and early diabetes. In the assessment of first-degree relatives for autoimmune diabetes, positive results in more than one of the marker antibodies (GAD, Islet cell, IA-2 or insulin) can be associated with the onset of autoimmune diabetes. GAD65 antibodies are seen in 70-80% of Caucasians with newly diagnosed type 1 diabetes. GAD65 antibodies are higher and more common in patients with other associated autoimmune disorders such as thyroiditis. Note: Negative GAD antibody results (<5.0 U/mL) are referred for further testing as follows: • IA2 antibody • ZNT8 antibody

Requestable Seperately?Yes

Minimum Sample Volume:0.5mL

Expected Turnaround Time:Frequency of testing: Weekly Target: 7 days

Test Code:GAD

Sample Type:

Serum Gel Tube (Gold top)

Complex Reference Range:<5 U/mL = Negative

Collection Conditions / Other Information:1st class post or Transport

Referred to Another Laboratory?No

Storage Requirements:Ambient temperature

NPEX / PDF Reporting Available:Yes

EQA Scheme:Yes

Further information:Performed in place of Islet cell antibody requests. Note: Negative GAD antibody results (<5.0 U/mL) are referred for further testing as follows: • IA2 antibody • ZNT8 antibody

Lead Contact Details:rwh-tr.bcpsimmunologyclinicalqueries@nhs.net

Email Address For Chasing Results:rwh-tr.ImmunologyLab@nhs.net

Methodology:ELISA

Site Sample Tested:Immunology, New Cross Hospital, Wolverhampton

Minimum Request Interval (MRI):180 days (6 months) over 16y only