A clinical algorithm to determine the etiology of brittle diabetes.

Brittle diabetes is a subset of insulin-dependent diabetes mellitus for which multiple causes have been suggested. In its most severe form, brittle diabetes is incapacitating, preventing gainful employment and a normal lifestyle. Although some brittle diabetic individuals will significantly improve by intensive insulin therapy and education, many others remain unable to function normally because of recurrent episodes of hyperglycemia and hypoglycemia. We studied 30 incapacitated brittle diabetic subjects and developed an efficient algorithmic approach to determine the etiology of brittleness. Central to our diagnostic algorithm was the glucose response to 0.1 U/kg insulin administered subcutaneously and intravenously. If this response was normal, then psychosocial evaluations were completed, including psycholinguistic and health psychological testing. Other parameters affecting blood glucose concentration were also assessed, such as gastric motility, counterregulatory hormones, and, most important, patient compliance with prescribed regimens. However, if an "abnormal" glucose response to the insulin challenge tests was observed, the location of the insulin resistance was identified as being subcutaneous, intravascular, or at the peripheral tissue. Using our diagnostic algorithm, the identification of the etiology of brittleness in 29 of the 30 referred patients was possible. Thus, the purpose of an algorithmic approach to diagnosis is not only to avoid unnecessary testing, but also to determine the correct etiology of the brittle diabetes to determine appropriate therapy.