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Investigating the accuracy and safety data behind CGM devices in the UK

John Pemberton is a Paediatric Diabetes Dietitian who also lives with type 1 diabetes. Working with leading researchers, he compared how different countries decide which continuous glucose monitoring (CGM) devices should be made available, and for who. Here, John shares why he wants people with type 1 diabetes to know more about the data behind their devices, so everyone can be confident their tech meets the very best standards.


John Pemberton
John Pemberton

I'm a Paediatric Diabetes Dietitian living with type 1 diabetes, leading the CGM device service at the Birmingham Children's Hospital, which supports over 300 children with type 1 diabetes. And I am concerned that some continuous glucose monitoring (CGM) devices available for people living with type 1 diabetes in the UK do not have sufficient accuracy and safety data publicly available.

This is despite CGMs having CE marking, which confirms that they meet certain essential requirements of the European Commission. CGM devices can be sold in the UK if they have CE marking, therefore CE marking is unwittingly considered a reliable marker of CGM device accuracy and safety for healthcare professionals, funders and people living with type 1 diabetes. 

I'm hoping to raise awareness of this and foster a desire in the diabetes community to get it changed. 

NICE guidelines and accuracy

My concern has escalated since the National Institute for Clinical Excellence (NICE) updated its guidance for CGM usage in March 2022, recommending that everyone living with type 1 diabetes should have access to either CGM or Flash (another type of wearable glucose monitor) on the NHS.

This makes the UK market attractive to manufacturers offering CGM devices with varying accuracy and functionality.

The NICE guidance states that the accuracy of the CGM device should be the first consideration. However, it provides no guidance on assessing CGM accuracy, and CE marking is thought to be reliable.

Once deemed accurate and comparable, the NICE guidance recommends selecting the cheapest CGM device. Therefore, understanding if CE marking is reliable for accuracy and safety is essential.

What did I do?  

I contacted leading researchers in the UK and Europe for their help. We decided to review the CE marking system and compare it to the approvals process used by the regulatory body in the USA - the Food and Drug Administration (FDA), and Australia's Therapeutic Goods Administration (TGA).

The manufacturers of CGM devices trading in the UK provided the clinical data supporting their CE marking for type 1 diabetes. We reviewed this data against the FDA's tighter approvals process for CGMs, which are the most robust measures currently available. 

What are the main results? 

The USA FDA and Australian TGA approval are reliable markers for CGM device accuracy, performance and safety. They use a more robust assessment criteria that requires clinical data on each specific device.

In contrast, CE marking is not a reliable marker for the accuracy and performance of CGM devices. There are no standardised criteria and when deciding on which type of diabetes and the age range of people who the device should be approved for, the agencies accept a small sample of clinical data and data from a similar device. 

This has led to CGMs including the GlucoMen Day, GlucoRx Aidex, and Medtrum TouchCare Nano being approved for children with type 1 diabetes despite having no publicly available clinical data on that age group. Also, the GlucoRx Aidex is available for adults with type 1 diabetes based on a study where more than 80% of participants had type 2 diabetes. 

Assessment of CGM device clinical data against the FDA’s iCGM Criteria showed that two devices meet the accuracy standards for adults and children with type 1 diabetes:

  • Dexcom ONE, Dexcom G6 and Dexcom G7
  • FreeStyle Libre 2 and FreeStyle Libre 3

What are the next steps? 

We want to present this information to the UK national regulator, the Medicines and Healthcare products Regulatory Agency (MHRA). The MHRA can ask manufacturers for the missing clinical data if CE marking recommendations stretch beyond the publicly available clinical data.

The MHRA can remove unsupported approval for specific ages and diabetes types if they think it's necessary. For example, without clinical data supporting, the MHRA could remove the approval for children with type 1 diabetes from the GlucoMen Day, GlucoRx Aidex, and Medtrum TouchCare Nano.

The MHRA could also remove the approval for type 1 diabetes adults from the GlucoRx Aidex. Removal of unsupported approval for specific populations would prevent health care professionals and funders from selecting one of the above devices based on cost despite the CGM device's insufficient publicly available clinical data.

You can read our full report and if you want to see positive regulatory change, you can add your contact details and join #WeDeserveBetter. 

About John

John Pemberton is a Paediatric Diabetes Dietitian at Birmingham Children's Hospital who helps empower children to self-manage their diabetes. He was diagnosed with Type 1 diabetes in 2008 and currently uses the Dexcom G6 and Medtronic VEO Pump.

He is the creator of the award winning 'CGM Academy', which teaches dynamic glucose management. He is a co-author on the International Society for Pediatric and Adolescent Diabetes 2022 exercise guidelines. He co-created the award-winning virtual schools' diabetes teaching program in response to Covid-19. His favourite creation is the education program he has set up for his family, in case his children develop type 1 diabetes. 

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