To be included in the study, a family had to have at least one ASP available for sampling; availability of one or both biological parents was preferred but not required. For families, trios and cases, an individual was designated as affected with type 1 diabetes (T1D) if he or she had documented T1D with onset at <35 years of age, had used insulin within 6 months of diagnosis, and had no concomitant disease or disorder associated with diabetes.