Objective To evaluate the performance of the FreeStyle Libre Flash continuous glucose monitoring (FSL-CGM) system against established central laboratory methods.
Research design and methods 20 subjects (8 type 1 diabetes mellitus, 12 type 2 diabetes mellitus) were analyzed. FSL-CGM sensor measurements (inserted in arm and abdomen) were compared with capillary blood glucose results analyzed with StatStrip as semigold standard. The glucose response after a standardized oral glucose load was measured by FSL-CGM and capillary samples analyzed by perchloric acid hexokinase (PCA-HK) method, StatStrip and FSL test strip (FSLC), and a commonly used CGM system (iPro2).
Results FSL-CGM arm sensor readings showed 85.5% of paired readings falling within Clarke Error Grid (ISO 15197:2013) zone A when compared with StatStrip. For FSL-CGM abdomen and FSLC, these percentages were 64% and 98%, respectively. The overall correlation of FSL-CGM in the arm and the StatStrip indicates a performance with lower results with the FSL-CGM in the arm than expected based on the StatStrip in the lower glucose ranges, and higher results than expected in the higher ranges. Following a standardized glucose load, a slower rise in glucose level was observed for FSL-CGM arm as compared with PCA-HK, StatStrip, FSLC, and iPro2 during the first 45–60 min after glucose load ingestion.
Conclusions Certain matters need attention while using the FSL-CGM in daily life including the observed lower values in the lower ranges, and the underestimation of the effect of a meal on glucose response. These effects of such deviations can partly be overcome by optimizing the available user instructions.
Trial registration number TC5348; results.
- Blood Glucose Self-Monitoring
- Continuous Glucose Monitoring
- Endocrinology Diabetes
- Glucose Control
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Contributors MJF wrote protocol, practical examination, researched data, wrote manuscript, contributed to discussion. SA was involved in practical examination, researched data, reviewed/edited manuscript. MAE, DdJ and PRvD researched data, contributed to discussion, reviewed/edited manuscript. RS contributed to discussion, reviewed/edited manuscript. HJGB wrote protocol, contributed to discussion, reviewed/edited manuscript.
Funding This study was supported by an unconditional grant of the Stichting Achmea Gezondheidszorg (SAG).
Competing interests None declared.
Ethics approval Ethics Review Committee of the Hospital Isala, Zwolle.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement The authors agree on data sharing with regard to this manuscript. More data are available of subjects without diabetes, and the influence of paracetamol and vitamin C on the performance of the FSL (see also www.trialregister.nl (TC 5348)).
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