Islet Cell autoantibodies
Distinguishing type 1 from type 2 diabetes mellitus
Identifying individuals at risk of type 1 diabetes (including high-risk relatives of patients with diabetes)
Predicting future insulin requirement treatment in patients with adult-onset diabetes
Negative results do not exclude the diagnosis of or future risk for type 1 diabetes mellitus. The risk of developing type 1 diabetes may be stratified further by testing for HLA genetic markers. Careful monitoring of hyperglycemia is the mainstay for determining the requirement for insulin therapy.
GAD65 antibody: Monday through Friday
Insulin antibodies: Monday, Wednesday, Friday
IA-2 antibody: Tuesday, Thursday
Zinc Transporter 8 Antibody: Tuesday, Thursday
GD65S, INAB, IA2: Radioimmunoassay (RIA)
EZNT8: Enzyme-Linked Immunosorbent Assay
DMEI: Interpretive Comments
GLUTAMIC ACID DECARBOXYLASE (GAD65) ANTIBODY
< or =0.02 nmol/L
Reference values apply to all ages.
ISLET ANTIGEN 2 (IA-2) ANTIBODY
ZINC Transporter 8 (ZnT8) ANTIBODY
< 15.0 U/mL
Seropositivity for 1 or more islet cell autoantibodies is supportive of:
-A diagnosis of type 1 diabetes. Only 2% to 4% of patients with type 1 diabetes are antibody negative; 90% have more than 1 antibody marker, and 70% have 3 or 4 markers.(1) Patients with gestational diabetes who are antibody seropositive are at high risk for diabetes postpartum. Rarely, diabetic children test seronegative, which may indicate a diagnosis of maturity-onset diabetes of the young in clinically suspicious cases.
-A high risk for future development of diabetes. Among 44 first-degree relatives of patients with type 1 diabetes, those with 3 antibodies had a 70% risk of developing type 1 diabetes within 5 years.(2)
-A current or future need for insulin therapy in patients with diabetes. In the UK Prospective Diabetes Study, 84% of those classified clinically as having type 2 diabetes and seropositive for glutamic acid decarboxylase 65 required insulin within 6 years, compared to 14% that were antibody negative.(3)