Prevalence of Islet Autoantibodies in Adults Without Diabetes

Over half of all new cases of type 1 diabetes (T1D) are diagnosed in adults, yet the natural history of adult-onset T1D, particularly in nonfamilial populations, is not fully understood.

This study measured the prevalence of islet autoantibodies (IA) in adults without known diabetes and irrespective of T1D family history from Colorado (USA).

The Autoimmunity Screening for Kids study screened for IAs to insulin, glutamic acid decarboxylase (GADA), islet antigen-2, and zinc transporter 8 in 1087 adults without known diabetes [mean age 40.7 years with range 19.6-63.9 years, 63% non-Hispanic White (NHW), 10% with family history of T1D in a first-degree relative, and 78% female] from Colorado. IAs were measured using radiobinding assay and electrochemiluminescence detection methods.

In total, 3.86% of adults screened positive for any IA, 0.55% screened positive for multiple IAs, and 1.75% were positive for a single IA by both detection methods. Compared to NHW, those with Hispanic race/ethnicity were more likely to screen positive for a single IA (relative risk 2.32, 95% confidence interval 1.40, 3.84, P = .001), but there was no difference in the risk of screening positive for multiple IAs when comparing across race/ethnicity. GADA was the most prevalent IA, found in 2.67% of adults.

IA prevalence was high in this sample of adults without known diabetes from Colorado. Further study is needed to fully characterize the risk of progression to clinical diabetes among adults who screen positive for IAs, particularly in nonfamilial populations.