Medical device manufacturers come across the concept of “classification” in various different contexts: when developing devices and having them authorized, when structuring organizations, and when writing scientific texts.
In this article you will learn:
The task of classification is to define classes – also called categories – and to assign elements to these classes.
Strictly speaking, classification and classing are different:
Forming classes by defining common characteristics. It is the same as creating categories and, therefore, is also called categorization.
Classing is the assignment of elements to the previously defined classes based on their features and classification rules.
However, in everyday language, we don’t differentiate between classification and classing and use the term “classification” for both.
Medical device manufacturers must constantly:
Two things can go wrong with classifications:
Both errors can be very damaging for manufacturers, as the following examples show:
Classification according to Annex VIII of the MDR
The MDR and MDCG (esp. 2019-11 and 2021-24) establish unclear and sometimes contradictory classification rules for software.
There have been arguments, all the way through to legal disputes, between manufacturers and authorities/notified bodies.
The EMDN is not comprehensive or ambiguous, for example, in the case of non-active accessories for active devices.
Manufacturers cannot assign their products to a class. The authorization application fails.
Severity of harm in risk management
Manufacturers do not precisely define the rules for the division of severities in risk management. For example, they define serious harm as a “serious impairment of health.”
Delayed submission and authorization
The preparation of the risk analysis takes a disproportionately long time because there is no consensus on when harm is considered a “serious impairment of health.”
Furthermore, the notified body questions the division of specific risks. The result is a delayed submission.
Structure of the technical documentation
The manufacturer submits the technical documentation electronically. A reader cannot tell from the directory structure (a hierarchical classification) whether the usability test report can be found in the “Usability” directory or in the "Verifications and validations” folder.
The manufacturer's team itself does not know which directories data should be stored in. This leads not just to arguments, it also leads to documents not being submitted or documents being submitted when they are not needed, sometimes even in different versions in different directories.
The notified body cannot find the documents and writes a deviation because the very first requirement of Annex II of the MDR/IVDR (“clear, organised, readily searchable and unambiguous manner”) has not been met.
Structure of the company
The organizational structure and workflows do not assign responsibilities and decision-making powers to roles and departments in a way that is clear and comprehensible to everyone.
Non-conformity, loss of customers
Different departments bicker about who is responsible for doing something and who is accountable for it. Arguments start. Customers do not know who they should contact. The organization does not adequately meet their needs, so they find another company.
When you define classes or categories precisely, you show that you have really understood a domain. You create clarity. And clarity creates effectiveness and efficiency.
And with clarity, common problems can be avoided:
The division of concepts into classes is like modeling. These models are simplified representations of the world through which you can understand things. For example, models help to identify and eliminate the real causes of problems.
Models also help to formalize knowledge.
Make sure that you fully map the domain with your classes.
Classification, like all modeling, must be fit for purpose.
However, for an oncologist, the class “malignant neoplasms” is not very helpful as all their patients fall into this class. They need a much more detailed and nuanced grouping to be able to decide on the right therapy.
The classification should maintain its inherent logic, such as the dimension and the system behind the division.
To allow a clear assignment of concepts to classes, the classification rules must ensure unambiguous and reproducible assignment. This is not a minor issue, since the world cannot always be represented as classes or hierarchical classes, i.e., as a tree.
There are different approaches for determining which class certain concepts should be assigned to. We differentiate between:
Intensional grouping has the advantage that it does not have to be adapted, i.e., expanded, in the event of new elements, as is the case with extensional groupings.
However, intensional grouping has the disadvantage that divisions occur because rules are missing or are not suitable for the new element.
The rules and thus classification characteristics must be unambiguous and unarguable. Therefore, we recommend combinations of binary criteria for which an unarguable decision can be made.
The classification rules must be understood by the people who are responsible for the classification (more precisely, the classing). Therefore, unclear terms and examples must be avoided.
Finally, you must ensure the “usability” of your classification rules. In hierarchical classification systems (taxonomies), for example, this means:
People say a lot about their thinking through the way they represent the world, how they divide it into categories and classes. Even the directory structure on a drive or the section structure of a document reveals a lot about the owner or author.
Precise classification creates precise models. They, in turn, provide clarity, without which demanding activities such as device development or managing an organization successfully become almost impossible.
Therefore, it is worth taking the time to create a precise classification.
The Johner Institute helps medical device manufacturers and their service providers gain clarity: from the qualification and classification of their devices, to the structure of their technical documentation, through to successful authorization (German) and post-market surveillance.