Continuous glucose monitoring: an overview of today's technologies and their clinical applications.

The first glucose sensors that allow continuous glucose monitoring are now available. It is important that physicians understand the special clinical and technical aspects that are key to successful implementation of these sensors--and of other sensors being under clinical development--into the daily practice of patients with diabetes. One important question is whether under all circumstances changes in blood glucose are paralleled by glucose changes in the interstitial fluid, in terms of both absolute values and time. Only if this is the case can measuring glucose in the interstitial fluid be a reliable substitute for measuring blood glucose. Usually, glucose sensor readings of interstitial fluid are transformed by means of a calibration process, so that the readings show actual blood glucose levels and not the interstitial glucose levels. If the calibration factor is inaccurately estimated, this error would be perpetuated with potential clinical implications. Patients with diabetes have to learn the proper use of the individual glucose sensor system, including its calibration and quality control. They also have to be informed about the problems and limitations of each sensor. Continuous monitoring should supply the patients with all information required to optimise their insulin therapy. The relatively high costs of glucose sensor systems should be viewed in the context of the potential optimisation of metabolic control, which should ultimately reduce the costs for the treatment of late complications of diabetes. These reduced costs would clearly far outweigh the costs of self-monitoring and self-control. Clinical trials are necessary to clearly demonstrate the long-term benefits of continuous glucose monitoring. The development of glucose sensors has now reached a stage at which it is important to address such questions appropriately.