Standardization process of continuous glucose monitoring: Traceability and performance

People with diabetes are required to regularly check their glucose to make therapy decisions. So far, systems for self-monitoring of blood glucose were used, but nowadays minimally invasive continuous glucose monitoring (CGM) systems are increasingly more often employed, sometimes to partially replace self-monitoring of blood glucose. Most CGM systems on the market measure glucose concentrations continuously in the interstitial fluid of the subcutaneous fatty tissue. However, CGM has a principle limitation. Collecting interstitial fluid frequently in sufficiently large volumes over short time periods is not easy. As a consequence, no internationally accepted reference measurement procedure is currently available for glucose in interstitial fluid which is a prerequisite to achieve an optimal metrological traceability. Recent studies indicate that the analytical performance of minimally invasive CGM systems differs not only between manufacturers but also between individual sensors of the same system, sometimes even in the same subject. Because manufacturers don't provide detailed information about the traceability chain and the measurement uncertainty of their systems glucose values obtained with CGM can currently not be adequately traced to higher-order standards or methods. Therefore, the Working Group on Continuous Glucose Monitoring aims at establishing a traceability chain for minimally invasive CGM systems, as well as procedures and metrics for the assessment of their analytical performance.