KEYSTONE, COLO. — Look for next-generation continuous glucose monitoring devices to be more accurate, less obtrusive, and easier for diabetic patients and their families to use, according to H. Peter Chase, M.D.
Among the numerous devices in development, he singled out two for purposes of illustration. Both are far along in the pipeline and provide a glimpse into a not-so-distant future in which continuous glucose monitoring is likely to transform diabetes management.
One of the devices, the TheraSense FreeStyle Navigator, is now under review by the Food and Drug Administration and likely will receive marketing approval in a year or so. The other, the DexCom G1, features a long-term implantable sensor half the size of a triple-A battery which is placed subcutaneously in the abdominal wall, where it measures glucose levels every 30 seconds and transmits the data wirelessly to a small receiver, Dr. Chase said at a conference on management of diabetes in youth.
Development of continuous glucose monitoring sensors is an extremely active area within the medical devices industry. Part of the impetus lies in a recognition that most patients really dislike self-monitoring blood glucose by fingerstick multiple times daily as part of intensive insulin therapy.
Indeed, studies show few patients do it as often as recommended. And even when they do, all they get are a series of snapshots of blood glucose levels at a few instants in time, hours apart, that tell nothing about how blood glucose fluctuates between tests.
In contrast, the DexCom G1 displays 1-, 3-, and 9-hour glucose trends and sounds an alert when real-time levels run low or high. Similarly, the FreeStyle Navigator's pocket-sized display monitor has a trend arrow that can point in five directions.
“This is ingenious. If the glucose is dropping fast, you want to know,” said Dr. Chase, professor of pediatrics at the University of Colorado, Denver.
TheraSense has petitioned the FDA to approve the device as a replacement for blood glucose testing, an indication for which neither of the two continuous glucose monitoring systems now on the market is approved. The company believes the technology it uses makes the Navigator more accurate at low glucose levels than currently devices.
But whether TheraSense receives its sought-after indication will depend in large part on the results of independent accuracy studies now being conducted by DirecNet, a National Institutes of Health-funded five-center consortium of which the university is a part.
Satish K. Garg, M.D., professor of medicine and pediatrics at the university, was the principal investigator in a recent clinical trial in which the DexCom device markedly improved glucose excursions compared with usual care in adults with type 1 diabetes.
For 30 days in the 90-day study, the 14 participating patients and their physicians were kept blinded to the sensor data. When they were unblinded and the sensor's alarm function was turned on—with alerts at glucose levels of 100 and 200 mg/dL and a continuous alarm at 55 mg/dL—their glucose profiles improved markedly.
Patients experienced a mean 37% increase in the number of hours per day spent with a glucose of 80-140 mg/dL, a 38% reduction in time spent at 40-55 mg/dL, and a 31% decrease in hours spent with a glucose level of 240-400 mg/dL compared with the blinded period.
Improved glucose profiles, over the long term, will substantially reduced rates of diabetic microvascular complications, Dr. Garg said at the conference, sponsored by the University of Colorado and the Children's Diabetes Foundation at Denver.