Continuous glucose monitoring: quality of hypoglycaemia detection

Abstract 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.