Incidence and significance of islet-cell autoantibodies in different types of diabetes mellitus.

Islet cell (ICA) and organ specific autoantibodies (OSA) were determined by the indirect immunofluorescence technique in 920 diabetics, 1,159 nondiabetic patients, and 100 young and 100 adult healthy controls with normal glucose tolerance. In control subjects ICA were not detected, and only 20 miscellaneous patients with normal glucose tolerance showed ICA (1.7%). ICA were present in 45.4% of patients with juvenile insulin dependent diabetes (IDD) during the first 6 mth of disease and in 29.1% of patients between 6 and 12 mth of disease onset; ICA presence decreased to 19.2% and 20.6% after 1 and 5 yr of duration of diabetes. In patients with maturity onset IDD, ICA incidence was 19.4% in the first year, 20% between 1 and 5 yr, and 12.2% after 5 yr of disease. In this group, 64% of ICA positive patients showed clinical and/or serologic evidence of thyroid, gastric, or adrenal autoimmune disorders. In sera from young patients with non insulin dependent diabetes (J NIDD), ICA were not detected. In adult patients with the same type of diabetes (M NIDD) ICA incidence was 9.8, 7, and 8.9% and was not related to the duration of diabetes. Patients with chemical diabetes were divided into 2 groups (younger and older than 35 yr), and ICA incidence was 18.9 and 12.9%, respectively. In 2 nondiabetic patients, glucagon cell autoantibodies were detected. ICA titers were variable in juvenile IDD of recent onset. Persistent ICA titers, frequently associated with OSA, were observed in the other types of diabetes, with the exception of J NIDD. ICA may be considered markers of severe beta cell alteration, with consequent reduction of insulin secretion, even though insulin dependency is sometimes delayed in a few patients.