International consensus on use of continuous glucose monitoring.
• Measurement of glycated haemoglobin (HbA1c) has been the traditional method forassessing glycaemic control. However, it does not reflect intra- and inter-day glycaemicexcursions that may lead to acute events (such as hypoglycaemia) or postprandialhyperglycaemia, which have been linked to both microvascular and macrovascularcomplications.
• Continuous glucose monitoring (CGM), either from real-time use (rtCGM) orintermittently viewed (iCGM), addresses many of the limitations inherent in HbA1c testingand self-monitoring of blood glucose. Although both provide the means to move beyondthe HbA1c measurement as the sole marker of glycaemic control, standardised metrics foranalysing CGM data are lacking. To address this issue and provide guidance in the use ofCGM data in clinical care and research an international panel of experts convened. Thisarticle intends to summarise their recommendations.
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• CGM is a robust research tool, and data from these systems should be recognised as avaluable and meaningful endpoint to be used in clinical trials of new drugs and devices fordiabetes treatment.
• Standardising glucose reporting and analysis is vital to facilitate effective clinical decision-making. Fourteen key metrics are suggested: 1. Mean glucose; 2. Percentage of time inlevel 2 hypoglycaemia (<54 mg/dL [3.0 mmol/L]); 3. Percentage of time in level 1hypoglycaemia (54–70 mg/dL [3.0–3.9 mmol/L]); 4. Percentage time in target range (70–180 mg/dL [3.9–10.0 mmol/L]); 5. Percentage of time in level 1 hyperglycaemia (>180mg/dL [10.0 mmol/L]); 6. Percentage of time in level 2 hyperglycaemia (>250 mg/dL [13.9mmol/L]); 7. Glycaemic variability, reported as coefficient of variation (primary) andstandard deviation (secondary); 8. Estimated HbA1c; 9. Data for glucose metrics reportedin three time blocks (sleep, wake, 24 hours); 10. Data sufficiency (a minimum of 2 weeksof data); 11. Data sufficiency: 70–80% of possible CGM readings over a 2-week period; 12.Episodes of hypo- and hyperglycaemia, using standard definitions; 13. Area under thecurve (recommended for research purposes); 14. Risk of hypo- and hyperglycaemia.
• Quantifying the duration and magnitude of glycaemic excursions provides another meansof assessing glucose control.
• The unifying theme of trials investigating the usefulness of CGM technologies is that thedevice must be worn on a near-daily basis to optimise its benefits.