Detection of hypoglycemia with continuous interstitial and traditional blood glucose monitoring using the FreeStyle Navigator Continuous Glucose Monitoring System

Diabetes Technol Ther. 2009 Mar;11(3):145-50. doi: 10.1089/dia.2008.0047.


Background: The objective of the analysis was to compare detection of hypoglycemic episodes (glucose <70 mg/dL lasting >15 min) with the FreeStyle Navigator 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.

MeSH terms

  • Adolescent
  • Adult
  • Biosensing Techniques
  • Blood Glucose / analysis*
  • Body Mass Index
  • Diabetes Mellitus, Type 1 / blood*
  • Female
  • Humans
  • Hyperglycemia / diagnosis*
  • Hyperglycemia / epidemiology*
  • Male
  • Monitoring, Ambulatory / instrumentation
  • Monitoring, Ambulatory / methods*
  • Sensitivity and Specificity
  • Time Factors
  • Young Adult


  • Blood Glucose