Resistance to data loss from the Freestyle Libre: Impact on glucose variability indices and recommendations for data analysis

Andrew P Kingsnorth, Maxine E Whelan, Mark W Orme, Ash C Routen, Lauren B Sherar, Dale W Esliger

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    2 Citations (Scopus)
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    Like many wearables, flash glucose monitoring relies on user compliance and is subject to missing data. As recent research is beginning to utilise glucose technologies as behaviour change tools, it is important to understand whether missing data are tolerable. Complete Freestyle Libre data files were amputed to remove 1–6 h of data both at random and over mealtimes (breakfast, lunch, and dinner). Absolute percent errors (MAPE) and intraclass correlation coefficients (ICC) were calculated to evaluate agreement and reliability. Thirty-two (91%) participants provided at least 1 complete day (24 h) of data (age: 44.8 6 8.6 years, female: 18 (56%); mean fasting glucose: 5.0 6 0.6 mmol/L). Mean and continuous overall net glycaemic action (CONGA) (60 min) were robust to data loss (MAPE ≤3%). Larger errors were calculated for standard deviation, coefficient of variation (CV) and mean amplitude of glycaemic excursions (MAGE) at increasing missingness (MAPE: 2%–10%, 2%–9%, and 4%–18%, respectively). ICC decreased as missing data increased, with most indicating excellent reliability (>0.9) apart from certain MAGE ICCs, which indicated good reliability (0.84–0.9). Researchers and clinicians should be aware of the potential for larger errors when reporting standard deviation, CV, and MAGE at higher rates of data loss in nondiabetic populations. But where mean and CONGA are of interest, data loss is less of a concern. Novelty: As research now utilises flash glucose monitoring as behavioural change tools in nondiabetic populations, it is important to consider the influence of missing data. Glycaemic variability indices of mean and CONGA are robust to data loss, but standard deviation, CV, and MAGE are influenced at higher rates of missingness.

    Original languageEnglish
    Pages (from-to)148-154
    Number of pages7
    JournalApplied Physiology, Nutrition, and Metabolism
    Issue number2
    Early online date19 Aug 2020
    Publication statusPublished - Feb 2021

    Bibliographical note

    Copyright © and Moral Rights are retained by the author(s) and/ or other copyright owners. A copy can be downloaded for personal non-commercial research or study, without prior permission or charge. This item cannot be reproduced or quoted extensively from without first obtaining permission in writing from the copyright holder(s). The content must not be changed in any way or sold commercially in any format or medium without the formal permission of the copyright holders.


    • Data loss
    • Flash glucose monitoring
    • Freestyle Libre
    • Glycaemic variability
    • MHealth
    • Self-monitoring

    ASJC Scopus subject areas

    • Endocrinology, Diabetes and Metabolism
    • Physiology
    • Nutrition and Dietetics
    • Physiology (medical)


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