Studies [Cou03] on stored blood from identical twins, one of whom subsequently developed juvenille diabetes has revealed that the affected twins blood showes evidence of antibodies against insulin producing cells for a considerable period prior to the development of overt diabetes. Three specific antibodies have been identified;
People who have at least one of these three antibodies have a 25% chance of developing diabetes in the next five years. If the subject has more than one antibody or actually shows a slownees in clearing a load of glucose from the blood then the chance of full blown diabetes within 5 years rises to 90%.
However, it must be born in mind that many people who have the antibodies will never become diabetic.
Trials of new treatments of Diabetes Mellitus often target people with newly diagnosed Diabetes as these are easier to identify than people with increased risk of developing Diabetes.
The potential disadvantage of targeting people with newly diagnosed diabetes is that the destruction of the pancreas is nearly complete and a treatment that may work in people at an earlier stage, will be of no effect. Thus the treatment will be written off when it may be of use to people who are at increased risk of developing diabetes.