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Editorial

Standardization of continuous glucose monitoring

Over the last years, continuous glucose monitoring scientifically sound study and analytical procedures
(CGM) as an alternative or addition to conventional blood to test CGM accuracy. So far, procedures to improve
glucose monitoring (BGM) has been gaining more and reference measurements were developed [6] as well as
more importance for patients with diabetes mellitus. a method to statistically evaluate and display CGM
Nowadays, CGM and derived therapy parameters accuracy [7]. This work was supported by the IfDT
such as time in range (TIR) are an integral part of in cooperation with the Diabetes Center Berne in

many national and international therapy guidelines Switzerland based on long-standing experience
[1, 2]. However, unlike for BGM systems, there is and additional research activities. The definition of
no international standard that describes both test detailed study design and procedures including the
procedures and acceptance criteria for CGM systems. study population, requirements for inductions of
This leads to a variety of available CGM systems that glucose excursions, definition of suitable reference
differ not only in characteristics like sensor lifetime, measurements etc. is the next step. The aim is
application sites and device handling, but also regarding to provide standardized procedures that ensure
accuracy. Consequently, therapeutic decisions and representative and reproducible testing of all relevant
clinical outcomes, e.g. TIR, may vary depending on the aspects to improve consistency and transparency in
specific CGM system used. CGM accuracy reporting.
It is well known that there are different factors that If we use CGM derived parameters for therapy
have an influence on apparent accuracy assessed in assessment it is important to have accurate CGM
performance studies [3, 4]. These are, for example, systems without relevant bias.
the selected study population, distribution of glucose
values, frequency of reference measurements, reference Freckmann G.
measurement procedures and data evaluation. The
ultimate goal of CGM performance studies should be Guido Freckmann je ředitelem IfDT (Institut pro
to represent a CGM system’s accuracy in all situations technologie diabetu při Univerzitě v Ulmu) a předsedou
that occur in daily-life use, including a broad range of Pracovní skupiny IFCC pro kontinuální sledování
glucose values and high rates of change. However, in glukózy (WG-CGM). Zabývá se zejména analytickými
recent years, study protocols became less and less vlastnostmi CGM systémů a inzulinových pump.
challenging regarding study procedures. This allowed Je autorem desítek prací na tato témata publikovaných
manufacturers to obtain lower (i.e., better) mean v autoritativních odborných časopisech. Jeho alma
absolute relative difference (MARD) values as the market mater je Univerzita Goettingen.
is getting more and more competitive. In addition, when
CGM performance studies are published, comparisons References
between studies are often limited to accuracy results,
like the MARD values, without considering differences 1. American Diabetes Association. Standards of
in procedures. Medical Care in Diabetes. Diabet. Care, 2022, 45(Suppl
Apart from head-to-head studies, where different 1). [link]
CGM systems are tested in parallel in the same subjects, 2. Holt, R. I. G., DeVries, J. H., Hess-Fischl, A., Hirsch,
only standardized study procedures allow for adequate I. B., Kirkman, M. S., Klupa, T. et al. The management
comparison of different CGM systems. Therefore, of type 1 diabetes in adults. A consensus report by
in 2019, the International Federation of Clinical the American Diabetes Association (ADA) and the
European Association for the Study of Diabetes (EASD).
Chemistry and Laboratory Medicine (IFCC) created Diabetologia, 2021, 64(12), s. 2609-2652. [link]
a working group on CGM (WG-CGM). The aim of this 3. Reiterer, F., Polterauer, P., Schoemaker, M.,
working group is to develop standards for CGM studies Schmelzeisen-Redecker, G., Freckmann, G.,
including acceptance criteria and to eventually work Heinemann, L. et al. Significance and Reliability of
with the International Organization for Standardization MARD for the Accuracy of CGM Systems. J Diabet. Sci.
(ISO) on a guideline. Technol., 2017, 11(1), s. 59-67. [link]
The first topic which the working group has been 4. Heinemann, L., Schoemaker, M., Schmelzeisen-
R.,
Kassab,
G.,
Redecker,
A.,
Hinzmann,
working on was the establishment of traceability of Freckmann, G. et al. Benefits and Limitations of MARD
glucose values obtained by CGM to materials and as a Performance Parameter for Continuous Glucose
methods of higher metrological order [5]. As CGM Monitoring in the Interstitial Space. J Diabet. Sci.
systems measure glucose in the interstitial fluid, which Technol., 2020, 14(1), s. 135-50. [link]
cannot feasibly be sampled for reference measurements, 5. Freckmann, G., Nichols, J. H., Hinzmann, R.,
there is a break in the traceability chain. This break has Klonoff, D. C., Ju, Y., Diem, P. et al. Standardization
to be adequately addressed by manufacturers. process of continuous glucose monitoring: Traceability
and performance. Clin. chim. acta; Int. J. Clin. Chem.,
Currently, WG-CGM establishes suitable and 2021, 515, s. 5-12. [link]
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