King's College London

Research portal

Accuracy of Continuous Glucose Monitoring During Three Closed-Loop Home Studies Under Free-Living Conditions

Research output: Contribution to journalArticle

Hood Thabit, Lalantha Leelarathna, Malgorzata E. Wilinska, Daniella Elleri, Janet M. Allen, Alexandra Lubina-Solomon, Emma Walkinshaw, Marietta Stadler, Pratik Choudhary, Julia K. Mader, Sibylle Dellweg, Carsten Benesch, Thomas R. Pieber, Sabine Arnolds, Simon R. Heller, Stephanie A. Amiel, David Dunger, Mark L. Evans, Roman Hovorka

Original languageEnglish
Pages (from-to)801-807
Number of pages7
JournalDiabetes Technology and Therapeutics
Issue number11
Early online date4 Aug 2015
E-pub ahead of print4 Aug 2015
Published4 Nov 2015


  • dia_2E2015_2E0062

    dia_2E2015_2E0062.pdf, 398 KB, application/pdf

    Uploaded date:12 Feb 2016

    Version:Final published version

    Licence:CC BY

King's Authors


Objectives: Closed-loop (CL) systems modulate insulin delivery based on glucose levels measured by a continuous glucose monitor (CGM). Accuracy of the CGM affects CL performance and safety. We evaluated the accuracy of the Freestyle Navigator® II CGM (Abbott Diabetes Care, Alameda, CA) during three unsupervised, randomized, open-label, crossover home CL studies. Materials and Methods: Paired CGM and capillary glucose values (10,597 pairs) were collected from 57 participants with type 1 diabetes (41 adults [mean±SD age, 39±12 years; mean±SD hemoglobin A1c, 7.9±0.8%] recruited at five centers and 16 adolescents [mean±SD age, 15.6±3.6 years; mean±SD hemoglobin A1c, 8.1±0.8%] recruited at two centers). Numerical accuracy was assessed by absolute relative difference (ARD) and International Organization for Standardization (ISO) 15197:2013 15/15% limits, and clinical accuracy was assessed by Clarke error grid analysis. Results: Total duration of sensor use was 2,002 days (48,052h). Overall sensor accuracy for the capillary glucose range (1.1-27.8mmol/L) showed mean±SD and median (interquartile range) ARD of 14.2±15.5% and 10.0% (4.5%, 18.4%), respectively. Lowest mean ARD was observed in the hyperglycemic range (9.8±8.8%). Over 95% of pairs were in combined Clarke error grid Zones A and B (A, 80.1%, B, 16.2%). Overall, 70.0% of the sensor readings satisfied ISO criteria. Mean ARD was consistent (12.3%; 95% of the values fall within ±3.7%) and not different between participants (P=0.06) within the euglycemic and hyperglycemic range, when CL is actively modulating insulin delivery. Conclusions: Consistent accuracy of the CGM within the euglycemic-hyperglycemic range using the Freestyle Navigator II was observed and supports its use in home CL studies. Our results may contribute toward establishing normative CGM performance criteria for unsupervised home use of CL.

Download statistics

No data available

View graph of relations

© 2018 King's College London | Strand | London WC2R 2LS | England | United Kingdom | Tel +44 (0)20 7836 5454