Table 3.

Autoantibodies against islet autoantigens detected in stage 1–3 type 1 diabetes

Autoantibody	Islet specificity	Typical characteristics
IAA	Insulin	Common as a first detected autoantibody in young children (157,158) Appearance is more common in younger children (159) Frequency of appearance declines with age Not informative for individuals treated with insulin, who often develop antibodies in response to injected insulin
GADA	GAD	Common as a first detected autoantibody in childhood, up until age 15 years (157,158,160) Adult-onset cases most often present with GADA (161) Is associated with slower progression to T1D (162) and is often found as a single positive islet autoantibody, especially in adults
IA-2A (also known as ICA512)	Tyrosine phosphatase islet antigen-2	Presence is associated with more advanced islet autoimmunity and faster progression to stage 3 T1D (55,163)
ZnT8A	Zinc transporter type 8, a transmembrane protein in the β-cell granule	Presence can improve risk stratification in individuals with single GADA+, IAA+, or IA-2A+ status (164)
ICA	Multiple antigens, undefined	Detected by indirect immunofluorescence on islet cell tissue. While not frequently measured other than in research studies, it does add to risk determination in the presence of other biochemical autoantibodies

IA-2A, insulinoma antigen-2 autoantibody; ICA, islet cell autoantibodies; ICA512, islet cell autoantigen 512; T1D, type 1 diabetes.