Islet Autoantibody Seroconversion in the DPT-1 Study: Justification for repeat screening throughout childhood

OBJECTIVE: Although type 1 diabetes autoimmunity frequently begins in childhood, little is known about the relationship between age and autoimmunity development. Our aim was to determine the timing of seroconversion to diabetes-associated autoantibody (DAA) positivity and risk in first- and second-degree relatives of patients with type 1 diabetes. RESEARCH DESIGN AND METHODS: Study subjects were identified through the Diabetes Prevention Trial-Type 1 (DPT-1). Children 3–18 years of age (n = 42,447) were screened for DAAs; 1,454 were ICA positive (≥10 JDF units), 1,758 were GAD65 positive, and 899 were ICA512 positive at the time of initial screening. Subjects who were initially antibody negative (n = 39,212) were recalled for rescreening, and 11,813 returned for rescreening. RESULTS: DAA seroconversion occurred in 469 (4%) children; 258 seroconverted to ICA, 234 to GAD65, and 99 to ICA512. The median time to seroconversion was 2 years. The 2-year risk for DAAs was highest in early childhood. For each 1-year increase in age in this cohort, the risk of any autoantibody seroconversion (HR 0.95, 95% CI 0.92–0.97) decreased by 5%, and for any two autoantibodies risk decreased by 13% (0.87, 0.82–0.93). CONCLUSIONS: Risk of autoantibody seroconversion among children followed in DPT-1 is age dependent. Younger children have the highest risk for DAAs, with the majority of children seroconverting by 13 years of age (75%). This suggests that annual screenings should be started in early childhood and continued through early adolescence to identify the majority of subjects at risk for type 1 diabetes and eligible for prevention trials.