Detection of Hypoglycemia with Continuous Interstitial and Traditional Blood Glucose Monitoring Using the FreeStyle Navigator Continuous Glucose Monitoring System

Background: The objective of the analysis was to compare detection of hypoglycemic episodes (glucose <70 mg/dL lasting >15 min) with the FreeStyle Navigator (R) Continuous Glucose Monitoring System (FSN-CGM) (Abbott Diabetes Care, Alameda, CA) alarms to detection with traditional finger stick testing at an average frequency of eight tests per day. Methods: The performance of FSN-CGM alarms was evaluated in a clinic setting using 58 subjects with type 1 diabetes mellitus (T1DM) monitoring interstitial glucose concentration over a 5-day period compared to reference YSI measurements (instrument manufactured by YSI, Yellow Springs, OH) at 15-min intervals. Finger stick glucose testing was evaluated in the home environment with 91 subjects with TIDM monitoring with the blood glucose meter integrated into the FreeStyle Navigator (FSN-BG) over a 20-day period. The reference was FSN-CGM with results masked from the subjects. Blood glucose values <= 85 mg/dL were considered the optimal treatment level to avoid or reverse hypoglycemia. Results: With a threshold alarm setting of 85 mg/dL, 90.6% of hypoglycemic episodes were detected within +/- 30 min by FSN-CGM in the clinic study. When the alarm was activated, YSI glucose was <= 85 mg/dL 77.2% of the time. In the home environment, the average FSN-BG testing frequency was 7.9 tests per day. Hypoglycemia was verified within +/- 30 min by FSN-BG measurements <= 85 mg/dL at a rate of 27.5%. Conclusions: Even with a high rate of FSN-BG testing, hypoglycemia detected by FSN-CGM was verified by patients with T1DM very infrequently. A high rate of hypoglycemia detection with a moderate rate of unnecessary alarms can be attained using FSN-CGM.