Classifying a medical device is a manufacturer’s first regulatory decision. It determines the applicable conformity procedure, the level of documentation required, whether or not a notified body is needed, and the timelines to plan for. Getting the class wrong has direct consequences for the cost and the schedule of placing the device on the market.
The 4 risk classes
Class I. Low risk. Non-invasive devices or short-term invasive devices with no contact with vulnerable parts of the body, low-risk non-therapeutic active devices. Examples: plasters, corrective spectacles, crutches, stethoscopes. Conformity by manufacturer self-certification, except for the sub-classes below.
Three sub-classes require the intervention of a notified body, limited to their specific aspects (Article 52(7)): class Is (sterile devices) for establishing and maintaining sterile conditions, class Im (measuring function) for conformity with the metrological requirements, and class Ir (reusable surgical instruments) for aspects relating to reuse: cleaning, disinfection, sterilisation, maintenance, functional testing and the related instructions for use.
Class IIa. Moderate risk. Short-term invasive devices, active diagnostic devices, certain dental implants, contact lenses, hearing aids, cannulae. Notified body mandatory.
Class IIb. High risk. Long-term implantable devices not classified as III, active therapeutic devices, ventilators, defibrillators. Notified body mandatory with a more in-depth review.
Class III. Very high risk. Long-term implantable devices in contact with the heart, the central nervous system or the central circulatory system, absorbable devices with a systemic action. Coronary stents, heart valves, hip prostheses. Notified body mandatory, with assessment of the technical documentation of each device.
The logic of the 22 rules of Annex VIII
Annex VIII of the MDR organises the classification rules into four groups according to the nature of the device.
Rules 1 to 4: non-invasive devices. A general rule (class I by default) and special rules for channelling or storing blood and fluids (Rule 2), modifying the biological or chemical composition (Rule 3) and contact with injured skin or mucous membrane (Rule 4). Active devices fall under Rules 9 to 13.
Rules 5 to 8: invasive devices. Classification according to the nature of the invasion (body orifice or surgical), the duration of use (transient, short-term, long-term), and whether the device is active or passive.
Rules 9 to 13: active devices. Classification according to the effect on the body (diagnostic, therapeutic, energy), with Rule 11 specific to software.
Rules 14 to 22: special rules. Devices incorporating a medicinal substance or a human blood derivative (Rule 14), devices used for contraception or to prevent sexually transmitted diseases (15), disinfecting or cleaning devices (16), devices for recording X-ray diagnostic images (17), devices using tissues or cells of human or animal origin (18), nanomaterials (19), invasive devices intended to administer medicinal products by inhalation (20), substances absorbed by or locally dispersed in the body (21), active therapeutic devices with an integrated diagnostic function (22). Spinal implants and joint prostheses fall under Rule 8.
In the event of ambiguity or conflict between several rules applicable to the same device, the rule leading to the highest classification prevails.
What has changed compared with the directive
Several significant reclassifications came with the MDR. Rule 11 reclassified many software products from class I to higher classes. Reusable surgical instruments remain in class I but now fall into the Ir sub-class, which requires a notified body to assess the aspects relating to reuse. Rule 8 places spinal disc replacement implants and implantable devices in contact with the spinal column (except components such as screws, wedges, plates and instruments) in class III. Rule 22, for its part, covers active therapeutic devices with an integrated or incorporated diagnostic function that significantly determines patient management, which are classified as class III.
The MDR classification of a device must be verified independently of its previous classification under the directive. The former class does not transpose automatically.
Regulatory source: Annex VIII of Regulation (EU) 2017/745 — EUR-Lex