The accuracy and efficacy of real-time continuous glucose monitoring sensor in patients with type 1 diabetes

Diabetes Technol Ther. 2008 Oct;10(5):385-90. doi: 10.1089/dia.2007.0291.


Background: The accuracy and efficacy of the Medtronic Diabetes (Northridge, CA) Real-Time (RT)-Continuous Glucose Monitoring (CGM) sensor were analyzed in 72 subjects with type 1 diabetes.

Methods: This was a retrospective analysis of 60,050 temporally paired data points (sensor and glucose meter values) obtained during the course of an outpatient ambulatory study evaluating the efficacy of a sensor-augmented pump system in adults and adolescents. Subjects uploaded sensor values and self-monitoring blood glucose data to the CareLink Clinical Application (Medtronic Diabetes) via the Internet, every 2 weeks during the course of the study.

Results: The overall percentage of sensor readings within +/-20% or +/-30% agreement of reference glucose readings was 75.6% and 86.8%, respectively. The highest rate of agreement occurred in the 240-400 mg/dL range, where 79.9% of sensor readings were within +/-20% of meter values and 91.5% of sensor readings were within 30% of meter values. The mean absolute relative difference for all subjects was 15.8%, and the median absolute relative difference was 10.9%. The bias was -2.13 mg/dL. Paired glucose measurements from the RT-CGM and meter demonstrated that 95.9% of paired points in the overall subject population fell in zones A and B of the Clarke Error Grid. Consensus Error Grid Analysis established that 99.2% of paired data points were in zones A and B.

Conclusions: This study reports the accuracy of a continuous glucose sensor with a large number of paired data points (60,050). RT-CGM is safe and well tolerated and provides readings that are in close agreement with glucose meter values.

Publication types

  • Evaluation Study
  • Multicenter Study

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Blood Glucose / metabolism*
  • Blood Glucose Self-Monitoring / adverse effects
  • Blood Glucose Self-Monitoring / instrumentation*
  • Blood Glucose Self-Monitoring / standards
  • Child
  • Diabetes Mellitus, Type 1 / blood*
  • Female
  • Humans
  • Insulin Infusion Systems
  • Longitudinal Studies
  • Male
  • Middle Aged
  • Monitoring, Ambulatory / instrumentation
  • Reproducibility of Results
  • Retrospective Studies


  • Blood Glucose