Barbara Davis Center for Childhood Diabetes, University of Colorado Health Sciences Center, Denver 80262.
Several large clinical trials for the prevention of IDDM in islet cell antibody positive first-degree relatives are planned or underway. The design of these trials rests in part on assumptions about the natural history of autoimmunity during the prediabetic period and on the likely effectiveness of the intervention being tested. At this time, most of the factors that influence the required sample size can only be roughly estimated.