Clinical Trial Issues

Large-scale clinical trials have been very instrumental in the major advances in diabetes treatment and outcomes that have been achieved in the last 15-20 years. The first large clinical study, the University Group Diabetes Program (UGDP), which ended in 1970, reached the very controversial conclusion that use of the oral sulfonylurea, tolbutamide for the treatment of T2DM was associated with an increase in CVD mortality.48 Despite the controversy, the successful conduct of the UGDP was a major achievement. It illustrated that clinical trials of complex disease entities, such as diabetes, could be successfully conducted and paved the way for landmark intervention trials including the Diabetes Control and Complications Trial (DCCT), the United Kingdom Prospective Diabetes Study (UKPDS), and the Diabetes Prevention Program (DPP) that in the last two decades have generated the results that guide clinical care today.

From a current perspective, it is difficult to realize that until the DCCT (see Section was successfully completed, there was much uncertainty about the direct relationships between metabolic control and the development of microvascular complications. Indeed, it was commonly thought that glucose control was less important than genetic factors in placing individuals with diabetes at risk for complications. This uncertainty about the role of glycemic control was greatly confounded by the fact that, prior to the time that HbA1C and capillary blood glucose testing were available, efforts to derive integrated indices of metabolic control relied heavily on semiquantitative measures of urinary glucose.

Randomized controlled clinical trials have also been highly instrumental in demonstrating the effectiveness of new therapeutic options for the treatment or prevention of diabetic retinopathy (laser photocoagulation) and nephropathy (angiotensin-converting enzyme inhibitors (ACE-I) and angiotensin receptor blocking (ARB) drugs). Cardiovascular diseases account for two-thirds of the mortality of persons with diabetes. Compared with the general population, women with diabetes have an even greater relative risk for development of CVD than men. In the last three decades there have been major improvements in treatment of and reductions in mortality from CVD in the population at large. It has been more difficult to determine the effectiveness of various approaches to CVD prevention and treatment in persons with diabetes. In part, this has stemmed from early tendencies to preclude persons with diabetes from intervention trials because it was known that CVD was so highly prevalent and at younger age in individuals with diabetes. This trend has been reversed and individuals with diabetes (including women) are specifically included in ongoing CVD clinical trials.

Clinical trials in diabetes are difficult to conduct, expensive, labor intensive on both investigators and participants and, thus, require a significant commitment of resources. Often, long intervals of time are necessary to verify observational data or to measure the effects of therapeutic interventions on glycemic control or diabetic complications. Nevertheless, it is very likely that well-designed clinical trials will be necessary in the future as in the past.

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