The classification rules are the set of rules laid down in Annex VIII of Regulation (EU) 2017/745 that manufacturers use to determine a product’s risk class. The Annex consists of three chapters: Chapter I defines the terms, Chapter II sets out the implementing provisions, and Chapter III contains the 22 rules themselves, divided into four groups. The rules must be reviewed in full, and the outcome must be justified in the technical documentation, stating the rule applied. This entry describes the structure of the rule set; the resulting classes are addressed in the entry Risk classes of medical devices.
Definitions in Chapter I
Chapter I first defines the duration of use: transient means continuous use for less than 60 minutes, short-term means 60 minutes to 30 days, and long-term means more than 30 days. It also defines body orifice, invasive and surgically invasive device, reusable surgical instrument, and the distinction between active therapeutic devices and active devices for diagnostic and monitoring purposes. It further adds terms for particularly sensitive target structures—namely the central circulatory system and the central nervous system—each with a final list of the anatomical structures covered, as well as the concept of injured skin or mucous membrane. These definitions more often determine the class than the wording of the rules themselves.
Implementing provisions in Chapter II
Chapter II contains seven provisions governing application. The decisive factor is the intended purpose specified by the manufacturer, not actual use. Where devices are used in combination, each is classified separately; accessories are classified independently of the main device. Software that drives a device or influences its use falls into the same class as that device, whereas standalone software is classified on its own. If a device concerns multiple body parts, the use with the highest hazard potential is decisive. If more than one rule or sub-rule applies, the strictest rule applies and therefore the higher class. When calculating continuous duration of use, the immediate replacement of a device by a similar device must also be included.
The four rule groups in Chapter III
Chapter III groups the rules by device category. Section 4 contains Rules 1 to 4 for non-invasive devices, which start from the principle of Class I and, depending on contact with injured skin, channelling or storage of body fluids and their treatment, lead to higher classes. Section 5 contains Rules 5 to 8 for invasive devices, tiered by access route, duration of use and target structure; Rule 8 covers implantable and long-term surgically invasive devices, which generally fall into Class IIb, but breast implants, surgical meshes, joint prostheses and spinal implants fall into Class III. Section 6 contains Rules 9 to 13 for active devices, including the software rule (Rule 11) and the catch-all rule (Rule 13), under which all other active devices fall into Class I.
Special rules in Section 7
Section 7 contains Rules 14 to 22, which apply irrespective of device category and take precedence over the other rules insofar as they result in a higher class. Rule 14 assigns devices incorporating an ancillary medicinal substance to Class III. Rule 15 concerns devices for contraception or protection against sexually transmitted diseases; Rule 16 concerns devices for disinfection, cleaning or sterilisation of medical devices and for contact lens care; Rule 17 concerns devices for recording X-ray diagnostic images; Rule 18 concerns devices made from non-viable tissues or cells of human or animal origin, which generally fall into Class III. Rule 19 tiers devices containing nanomaterials according to internal exposure potential. Rule 20 covers devices for administering medicinal products by inhalation; Rule 21 covers substances introduced into the body and absorbed or distributed there; and Rule 22 covers active therapeutic devices with an integrated diagnostic function.
Distinction from case-by-case decisions and interpretative guidance
The rule set itself is binding EU law; interpretative guidance is not. The MDCG 2021-24 guidance explains the rules with examples and decision trees without changing the text of the Regulation. For borderline cases, there is also the coordination procedure among Member States known as the Helsinki Procedure. The related entry Rule 11 addresses the software rule as a case requiring particular interpretation and is not repeated here. Separate from classification is the prior question of whether a product falls within the scope of the Regulation at all. In disputes between the manufacturer and the Notified Body, the competent authority decides pursuant to Article 51(2).
Relevance for clinical trials
The rule applied has a direct impact on evidence planning because it determines the class, the evidence requirements and the involvement of a Notified Body. Particularly consequential are the provisions on intended purpose and on the strictest rule: a broadly worded indication can trigger a higher class and thus the requirement for a clinical investigation, whereas a precise intended purpose limits the evidence burden but may restrict marketing.
For this reason, rule assessment should be at the beginning of study planning, not at the end. Full-service CROs such as Mediconomics support manufacturers in aligning the classification rationale, intended purpose and clinical evidence strategy so that they remain robust in the conformity assessment procedure.
Frequently Asked Questions (FAQ)
What applies if multiple rules are applicable?
Under Chapter II, Section 3.5, the strictest rule or sub-rule applies, meaning the highest class under consideration is decisive.
Is an accessory classified in the same way as the main device?
No. Accessories are classified separately and independently. Controlling software, by contrast, follows the class of the device it controls.
How is the duration of use calculated when devices are replaced repeatedly?
Chapter II, Section 3.6 requires that immediate replacement by a similar device be included in the calculation. Consecutive uses may therefore be considered long-term when taken together.
Regulatory References
- Regulation (EU) 2017/745, Annex VIII Chapter I, Definitions
- Regulation (EU) 2017/745, Annex VIII Chapter II, Implementing provisions 3.1 to 3.7
- Regulation (EU) 2017/745, Annex VIII Chapter III, Sections 4 to 7 with Rules 1 to 22
- Regulation (EU) 2017/745, Article 51(1) and (2) and Article 52
- MDCG 2021-24 Rev. 1, Guidance on classification of medical devices
