EASD e-Learning - Provided by leading diabetes academics

March 19, 2025 — 12:00 🕑 5 minutes

CGM systems reportedly failing – a plea for European quality standards

Recent reports of unreliable continuous glucose monitoring (CGM) systems highlight the urgent need for European standards to ensure the quality of these devices.

Chantal Mathieu, President of the European Association for the Study of Diabetes (EASD), together with other experts, is calling for a prompt introduction of minimum criteria for CGM systems to prevent substandard products from entering the market.

There is no doubt that continuous glucose monitoring (CGM) devices have greatly improved glycaemic control, both as stand-alone tools and in combination with insulin pumps or pens. However, with the increasing availability of affordable CGM systems, Europe is also facing the challenge of unreliable and error-prone devices entering the market, warns Chantal Mathieu, also Professor of Medicine at the Katholieke Universiteit Leuven in Belgium .

To ensure performance and accuracy standards, she and her colleagues propose a set of minimum criteria for a European “eCGM” compliance status in a recent publication in Diabetes, Obesity and Metabolism to be implemented without delay.

The rising need for CGM quality standards in Europe

The lack of quality standards in Europe has already affected people with diabetes. In 2022, for instance, clinicians in Italy’s Campania region raised concerns about the accuracy and reliability of a CGM system selected by health authorities. As a result, they advised against prescribing it, and people returned to traditional finger-prick blood glucose meters, including 20,000 people on intensive insulin therapy. For Mathieu, the message is clear: “It’s time for Europe to get its act together and establish quality criteria for CGM systems.”

“As clinicians, we must be confident in the robustness of CGM testing conducted by manufacturers. We advocate for a requirement that CGM sensors be tested in a population where 70–75% of participants have type 1 diabetes, ensuring their performance is assessed under conditions of rapid glucose fluctuations. These tests should include meal and insulin challenges, as well as a sufficient number of readings in both the hypoglycaemic and hyperglycaemic ranges,” says Mathieu, summarising the key requirements proposed for the market authorisation of CGM systems.

Defining minimum criteria: the eCGM concept

At present, new medical devices with a moderate to high risk profile – including CGM systems – are only required to undergo conformity assessment by a “Notified Body”, an organisation designated by EU or European Free Trade Association (EFTA) member states. Products that pass this process are awarded the CE (Conformité Européenne) mark, indicating compliance with general health and safety standards.

However, as Mathieu points out, the CE mark does not provide reliable information on the actual clinical performance of CGM systems. In fact, she and her co-authors argue that the current EU Medical Device Regulation (MDR) framework leaves considerable room for interpretation when it comes to clinical investigation as it does not provide CGM-specific requirements. They therefore propose that the eCGM framework should be mandatory for market authorisation. This includes several demands (Fig.1).

Figure 1: Proposed minimum set of requirements to validate the accuracy and performance of CGM systems prior to market authorisation. There are currently no CGM-specific guidelines for the evaluation of CGM systems in the EU and EFTA regions.

From glucose measurements to data security

The proposed validation requirements for CGM systems cover a wide range of issues. To assess performance, clinical investigations should reflect real-world use and glucose fluctuations, include all intended wear sites, and ensure reliable performance over the entire wear period. Trials should be conducted in each intended population, including a population with 70–75% of people with type 1 diabetes to test under variations in blood glucose levels. See the publication for detailed minimum performance requirements for different glucose ranges.

In addition, CGM sensors must demonstrate accuracy, even in the presence of clinically relevant potential interfering substances. The sensors used must provide reliable real-time glucose readings throughout the approved wear period, with safeguards to prevent use beyond this period.

In terms of data security and integrity, Mathieu and her colleagues suggest that real-time data transmission must be accurate and secure, with no treatment-relevant gaps in the flow of information. Data privacy and cybersecurity protections must comply with European data protection regulations. Finally, all data from clinical investigations should be fully disclosed and performance should be validated across multiple manufacturing lots.

A first step towards comprehensive regulation

While international experts point out that these requirements are only the most basic first steps needed, they are intended to provide an immediately applicable framework to ensure the quality of CGM systems entering the European market. In parallel, a working group of the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) is drafting ISO (International Organisation for Standardisation) standards for CGM systems, but this process is expected to take time.

“Our field is very concerned that healthcare payers could be deciding which CGM sensors to use based solely on cost, without any guarantee that these sensors will perform reliably,” says Mathieu of the current situation. In mid-2024, for example, the Association of British Clinical Diabetologists (ABCD) raised concerns about a CE-marked hybrid closed-loop (HCL) system that had been linked to hypoglycaemia. Despite the lack of performance data, the system was included in the England supply chain of the National Health Service (NHS).

“In the past, established manufacturers such as Dexcom, Medtronic and Abbott have generally provided robust clinical evidence for their systems,” explains Mathieu. „The real problem is that we currently have no way of distinguishing between reputable manufacturers and those bringing substandard products. There are simply no clear rules.” Without such stringent criteria, substandard products risk undermining patient safety and trust in these technologies.

The path forward for Europe

Eventually, Europe will need to adopt even stricter requirements than those proposed in the eCGM framework, says Mathieu, pointing to the US Food and Drug Administration (FDA) as a benchmark: “What we are proposing is a starting point, but ultimately, a regulatory framework similar to the one already in place at the FDA would be ideal. The FDA has clear criteria for the authorisation of CGM systems, and Europe should align with this standard.”

Such a framework would ensure that patients can fully benefit from the advances CGM systems have brought to diabetes management – without unnecessary risks to their safety.

Key Points:
European experts, including EASD President Chantal Mathieu, are calling for the introduction of minimum criteria for CGM systems entering the market.
Current CE marking requirements do not provide sufficient information on the actual clinical performance of CGM systems.
The proposed “eCGM” framework would require clinical investigations to reflect real-world CGM use and meet strict requirements for performance, accuracy, and data security and transparency.
International exports urge Europe to follow the example of the FDA, which has already established clear CGM-specific performance criteria.

Read this paper here.

Author: Hanna Gabriel, BA MSc. Any opinions expressed in this article are the responsibility of EASD e-Learning.

CGM systems reportedly failing – a plea for European quality standards

Recent News