The Diabetes Prevention Trial of Type 1 Diabetes (DPT-1)

The study was divided into three parts: screening, staging, and intervention. Subjects were recruited from study clinics and through media campaigns.First-degree relatives, 3 to 45 years of age, and second-degree relatives, 3 to 20 years of age, of patients with diabetes were screened for islet-cell antibodies. Those with an islet-cell antibody titer of 10 Juvenile Diabetes Foundation (JDF) units or higher were offered staging evaluations. Staging confirmed the presence of islet-cell antibodies, measured insulin antibodies, assessed the first-phase insulin response to intravenous glucose, assessed oral glucose tolerance, and determined the presence or absence of HLA-DQA1\*0102, DQB1\*0602, a protective haplotype, the presence of which excluded subjects from further participation. Islet-cell antibody-positive subjects were then defined as having a high risk of diabetes (a five-year risk of more than 50 percent) and were deemed eligible for the parenteral insulin trial if they had a first-phase insulin response below the threshold (as defined below) on two occasions, if their oral glucose-tolerance results were not completely normal,or both. Relatives who tested positive for islet-cell antibodies and insulin antibodies and who had a first-phase insulin response above the threshold and normal glucose tolerance were defined as having intermediate risk (a five-year risk of 26 to 50 percent) and were deemed eligible for the ongoing oral insulin trial. All randomized subjects were seen every six months, at which time an oral glucose-tolerance test was administered to assess glycemic status, the primary study end point. Mixed-meal tolerance tests were performed at base line, at years 1, 3, and 5, and at the end of the study. Intravenous glucose-tolerance testing was performed at years 2, 4, and 6 and at the end of the study.