The goal of the TrialNet Natural History Study of the Development of Type 1 Diabetes is to enhance our understanding of the demographic, immunologic, and metabolic characteristics of individuals at risk for developing type 1 diabetes.

The Natural History Study will screen relatives of people with type 1 diabetes to identify those at risk for developing the disease. Relatives of people with type 1 diabetes have about a 5% percent chance of being positive for the antibodies associated with diabetes. TrialNet will identify adults and children at risk for developing diabetes by testing for the presence of these antibodies in the blood. A positive antibody test is an early indication that damage to insulin-secreting cells may have begun. If this test is positive, additional testing will be offered to determine the likelihood that a person may develop diabetes. Individuals with antibodies will be offered the opportunity for further testing to determine their risk of developing diabetes over the next 5 years and to receive close monitoring for the development of diabetes.

In Screening , a simple blood test is done to screen for the presence of diabetes-related biochemical autoantibodies (GAD, IA-2A, mIAA). Islet cell autoantibodies (ICA) and ZnT8A are also measured in individuals positive for one or more biochemical autoantibodies. Participants will be provided with their screening results within 4-6 weeks.

If autoantibodies are present initially and are confirmed by repeat testing, participants will be invited to have additional testing in baseline monitoring visit to determine their average risk of developing diabetes over the next 5 years. The baseline monitoring visit will include an Oral Glucose Tolerance Test (OGTT), re-testing for biochemical and islet cell autoantibodies if needed, measurement of HbA1c, and HLA (genetic) typing.

Individuals with less than 3% average risk will be asked to come for follow-up on annual basis; individuals with greater than average 32% risk will be asked to come for follow-up visits on semi-annual basis.

Participants will be monitored for possible progression towards type 1 diabetes and may be offered the opportunity to enter into a prevention study such (e.g., Oral Insulin prevention study) or an early treatment study if they are diagnosed with type 1 diabetes while participating in the Natural History Study.