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FreeStyle Navigator Not as Precise as Other Glucose Meters

Jan 30, 2007

It may not be as accurate as a blood glucose monitor, but the results can provide important information to the patient as to what is happening, when they are not checking, it will be a great motivational tool! The FreeStyle Navigator continuous glucose monitoring system is not as accurate as the current-generation home glucose meters. However, investigators believe that the device has the potential to become an important addition to the treatment of children with type 1 diabetes.

"Direct reading, near-continuous, minimally invasive glucose sensors hold great promise for improving the care of patients with diabetes and other abnormalities of glucose metabolism," researchers point out in the January issue of Diabetes Care. "These sensors can provide both a measure of the current glucose concentration as well as glucose trends, with alarms for high and low thresholds and predicted hypo- and hyperglycemia."

Dr. Darrell M. Wilson and colleagues from the Jaeb Center for Health Research, Tampa, Florida, assessed the accuracy and precision of the FreeStyle Navigator continuous glucose monitoring system in 30 children with type 1 diabetes (mean age 11.2 years).

The Navigator glucose values were compared with reference serum glucose values of blood samples collected in an inpatient clinical research center and measured in a central laboratory using a hexokinase enzymatic method, and in an outpatient setting with a FreeStyle meter.

The team determined the median absolute difference and median relative absolute difference for sensor-reference and sensor-sensor pairs.

In a total of 1811 inpatient sensor-reference pairs, the median absolute difference between these measurements was 17 mg/dL and the median relative absolute difference was 12%.

For 8639 outpatient pairs, the median absolute difference and relative absolute difference was 20 mg/dL and 14%, respectively.

During the inpatient stays, the subjects simultaneously used two Navigator sensors resulting in 1971 Navigator-Navigator pairs. The mean relative absolute difference between these simultaneous measurements was 13%.

The researchers report that 91% and 81% of sensors in the inpatient and outpatient settings, respectively, had a median relative absolute difference no greater than 20%.

"After adjustment for glucose level, accuracy was significantly better at night for both inpatient and outpatient settings," Dr. Wilson and colleagues explain. "Accuracy was also significantly better for children 14 to 18 years of age during home use, but was not impacted by age during the inpatient visit."
Although the precision of the FreeStyle Navigator system does not yet match that of existing systems, the researchers believe it may eventually "become an important adjunct to treatment."

Diabetes Care 2007;30:59-64.


Doctor visits are approximately 16 minutes long on the average: that according to the National Center for Health Statistics. If a person with diabetes has an appointment once a month, that’s only 192 minutes spent with a doctor a year. This works out to 3.2 hours a year for face time with a doctor. For the other 8,760 hours of the year, patients must go it alone. For people with diabetes, this means that the majority of their care rests squarely on their own shoulders.