Continuous glucose monitoring: The next standard in diabetes care?

Continuous glucose monitoring devices have been available for some time, but they have been used primarily in patients whose diabetes is considered difficult to control. Also, convenience and accuracy issues limit several of the currently available devices.

Now, with new devices on the road to approval by the Food & Drug Administration, some diabetes experts are foreseeing continuous glucose monitoring as having the potential to transform diabetes management. In an effort to understand the devices' true potential to influence diabetes care, Drug Topics explored the advantages and limitations of current devices, the ways investigative devices might address those limitations, and the ways continuous monitoring, alone or in combination with insulin delivery, could change diabetes management.

Abbott Laboratories has submitted a continuous monitoring system, Freestyle Navigator, to the FDA for approval. The Freestyle Navigator obtains blood glucose readings every minute from a probe inserted subcutaneously. The system can store three days of glucose data.

The respective manufacturers of each system point out that the probe used in continuous glucose monitoring bypasses the multiple daily finger-sticks that many diabetics dread, and also provides more complete data than the conventional system, in which glucose readings occur several hours apart.

The currently available Minimed system is approved only for supplemental use and is recommended as a way to obtain more data and refine glucose control in patients with difficulties that cannot be elucidated by conventional testing. Abbott has applied for approval of its system as a replacement; the direction of Medtronic Minimed's application for approval of its combined system awaits data from clinical trials.

Whatever the outcome of these applications, they point to the potential for continuous glucose monitoring to become a standard in future diabetes care. In separate interviews with Drug Topics, company representatives and diabetes experts discussed the role of continuous glucose monitoring and its potential to advance diabetes management.

Replacing finger-sticks In the application submitted to the FDA for the Freestyle Navigator, Abbott is "hoping to get finger-stick replacement status," Abbott Laboratories spokesperson Heidi Calkins said. If so, the system would set a precedent in glucose monitoring. "We believe this system has the potential to have a significant impact on the lives of people with diabetes by providing instantaneous, real-time glucose readings." The system was originally developed by TheraSense in partnership with Abbott, and Abbott submitted a Pre-Market Approval (PMA) application for the device to the FDA in November 2003. Abbott acquired Thera Sense in April 2004.

The hair-thin probe can be inserted by the patient at home, and it should be free of irritation. It holds three days of information and is not sensitive to moisture or motion, Calkins said. "Patients should be able to exercise, perspire, and bathe while wearing it," she said. The sensor transmits the data by wireless technology to a pager-like receiver every 60 seconds. The patient can push a button to display the most recent glucose reading every 50 seconds. When the blood glucose reading is displayed, the receiver also displays an arrow to indicate whether the blood glucose is trending up or down.

"That's the beauty of the prod-uct's potential," she said. "By showing the trend, and by obtaining glucose levels every 60 seconds, you get a video instead of a snapshot. We hope that the system can therefore enhance self-care and reduce diabetes- and treatment-related complications."

Holly Kulp, R.D., the divisional VP of Navigator, pointed out that the clinical trial results resolved some accuracy issues that the FDA has raised about other continuous systems. "In one accuracy study of this system, 98% of the results were in the A and B zones of the Clarke Error Grid, and therefore were clinically accurate," she said. "In another home-use trial, patients had simultaneous readings with this system and 10 finger- or arm-sticks daily. After the data were unmasked, we found a 97.3% accuracy rate with the continuous monitoring system."