Continuous glucose monitoring: quality of hypoglycaemia detection

Diabetes Obes Metab. 2013 Feb;15(2):130-5. doi: 10.1111/dom.12001. Epub 2012 Sep 20.


Aims: To evaluate the accuracy of a (widely used) continuous glucose monitoring (CGM)-system and its ability to detect hypoglycaemic events.

Methods: A total of 18 patients with type 1 diabetes mellitus used continuous glucose monitoring (Guardian REAL-Time CGMS) during two 9-day in-house periods. A hypoglycaemic threshold alarm alerted patients to sensor readings <70 mg/dl. Continuous glucose monitoring sensor readings were compared to laboratory reference measurements taken every 4 h and in case of a hypoglycaemic alarm.

Results: A total of 2317 paired data points were evaluated. Overall, the mean absolute relative difference (MARD) was 16.7%. The percentage of data points in the clinically accurate or acceptable Clarke Error Grid zones A + B was 94.6%. In the hypoglycaemic range, accuracy worsened (MARD 38.8%) leading to a failure to detect more than half of the true hypoglycaemic events (sensitivity 37.5%). Furthermore, more than half of the alarms that warn patients for hypoglycaemia were false (false alert rate 53.3%). Above the low alert threshold, the sensor confirmed 2077 of 2182 reference values (specificity 95.2%).

Conclusions: Patients using continuous glucose monitoring should be aware of its limitation to accurately detect hypoglycaemia.

Publication types

  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Algorithms
  • Biosensing Techniques
  • Blood Glucose / metabolism*
  • Blood Glucose Self-Monitoring / methods
  • Blood Glucose Self-Monitoring / standards*
  • Diabetes Mellitus, Type 1 / blood*
  • Diabetes Mellitus, Type 1 / complications
  • Diabetes Mellitus, Type 1 / drug therapy
  • Female
  • Humans
  • Hypoglycemia / blood*
  • Hypoglycemia / diagnosis*
  • Hypoglycemic Agents / therapeutic use*
  • Male
  • Reproducibility of Results
  • Sensitivity and Specificity


  • Blood Glucose
  • Hypoglycemic Agents