Islet Cell Cytoplasmic Antibodies (ICA), IgG

Islet Cell Cytoplasmic Antibodies (ICA), IgG testing is used to classify new-onset diabetes and to differentiate autoimmune type 1 diabetes from other diabetes phenotypes at diagnosis. Detection of these anti-islet cell antibodies (islet cell cytoplasmic autoantibodies) also informs assessment of future type 1 diabetes risk, as seropositivity may precede clinical disease by months to years.

Serum autoantibodies to islet cell antigens indicate immune-mediated injury of pancreatic beta cells. Type 1 diabetes mellitus arises from autoimmune destruction of beta cells, resulting in insufficient insulin production, whereas type 2 diabetes is characterized predominantly by insulin resistance and lacks an autoimmune mechanism. Islet cell cytoplasmic antibodies are found in most individuals with autoimmune type 1 diabetes and are generally absent in type 2 diabetes. The emergence of ICA tracks with progressive loss of beta-cell function, the development of hyperglycemia, and the subsequent requirement for exogenous insulin therapy.