MDCG 2021-24 Guidance on classification of medical devices

Giovanni Di Rienzo

We have been longing for it since the MDR was first published and now eventually some guidance on device classification is available. Was it worth the wait? Well, to some extent it was.

The structure of the document is very similar to the structure of the MDD classification guidance (MEDDEV 2.4/1): there is a first part that describe the general principles to apply for a correct classification, followed by a series of flowcharts that provides a visual representation of the classification rules and by the guidance rule by rule with examples.

The first part does not seem to present major new concepts or principles. Most of the definitions presented are similar or identical to those in the text of the MDR or in MEDDEV 2.4/1. However there are some extra-clarifications regarding active devices, software and systems/procedure packs. And some new MDR terms, not defined within the regulation, are presented with a definition: those are mostly related to substances and absorption. Quite critical is the definition of the word “substance” that is crucial for classification under rule 21 but it is not specifically defined in the MDR (please note the definition of “substance” is not presented in the first part of the guidance together with the other terms but in the section dedicated to rule 21).

The heart of the document is the part with the guidance rule by rule and the examples. The number of examples is quite good and certainly increased as compared to MEDDEV 2.4/1. That is very good news because there is nothing like a good example to help decisions in difficult cases.

What is new, surprising or interesting there? It is a long and articulated document so it will take a while to digest it completely but here are a few things that we have noticed so far:

  • Accessories to AIMDs are all to be classified as class III under rule 8, whether they are active or non-active, implantable or not implantable. There had been a lot of discussions around those, and the hope was for a more pragmatic approach
  • Heart valve occluders and holders are specifically called out as class III under rule 6. So the argument that these devices are not intended specifically for use in direct contact with the central circulatory system but might just incidentally touch it, was not taken on by the MDCG group
  • Dental abutments are class IIb implantable devices under rule 8. Again there had been a lot of discussion if these should be classified under rule 5 or rule 8, if they should result in a class IIa or IIb classification and if they should be considered or not implantable devices. The guidance put the discussion to sleep, at least for the moment
  • The examples of software classification presented under rule 11, although not adding anything substantial to the guidance already published, are a good addition to try and bring some clarity
  • Under rule 18 (materials of human/animal origin) it is further emphasized that this rule does not apply to products made by animals (list of examples extended to include honey, propolis and royal jelly) and that the exclusion in case of presence of tallow derivatives does not apply when tallow represents a significant part of the device
  • Under rule 19 (nanomaterials) it is clarified that the expectation is for manufacturers to use the SCENIHR guidance document on the effect of nanomaterials (link), and in particular table 3 of this document, to estimate the potential for internal exposure. Careful though, this should be just “a starting point for correct classification”

There are certainly other new and surprising interpretations within the document and with time, dedication and some practical application they will come up but these are my initial thoughts.

All in all it is a useful document and we should be happy that it has been finally published. It is not perfect, we all agree on that, but it is hopefully just the first of a long series of updated versions.

If your device is not a me-too, classification was, is and will continue to be a tricky matter but if you need support to determine and substantiate the classification of your product, please get in touch with us at We will be more than happy to support you through this process. 


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