International clinical opinion on transparency, standardisation, and calibration alignment in the performance evaluation of systems for continuous glucose monitoring

Continuous glucose monitoring (CGM) is now central to diabetes management, yet variation in how respective medical products are evaluated limits meaningful comparison between CGM systems. Three barriers currently constrain reliable interpretation of glucose-derived measures. The first is limited transparency: in several regulatory settings, particularly those using Conformité Européenne marking, clinical-study reports, reference-method information and analytical documentation required for market authorisation are not publicly accessible. The second barrier is heterogeneity in study procedures. Existing evaluations use different reference-glucose methods, sampling strategies, glucose-manipulation protocols and participant characteristics, leading to accuracy estimates that cannot be interpreted consistently across systems. The third barrier is calibration alignment. Even with full transparency and aligned procedures, CGM systems may differ because their calibration algorithms are trained on distinct reference-glucose datasets, influencing reported glucose ranges, automated insulin-delivery behaviour and interpretation during device transitions. A modified Delphi process involving clinicians, laboratory scientists, and researchers identified these issues as the principal determinants of comparability. During this process, the International Federation of Clinical Chemistry and Laboratory Medicine released a validated framework for performance evaluation of CGM systems, providing a unified approach to reference-method selection, dynamic in-clinic testing, and structured reporting. Adoption would reduce procedural variability but does not resolve calibration-alignment differences. This international clinical opinion proposes a pathway towards internationally interpretable CGM evaluation: immediate transparency of clinical evidence, routine declaration of calibration alignment, and progressive adoption of validated standardised procedures. These steps provide a foundation for reliable interpretation and globally comparable assessment of CGM technologies.