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, non-sterile reusable surgical instruments, crutches, stethoscopes. Conformity by manufacturer self-certification.
Two specific sub-classes require the partial intervention of a notified body: class Is (sterile) for sterilisation aspects only, and class Im (measuring function) for metrological aspects only.
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 a design examination.
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 devices in contact with wounds, with blood or bodily fluids, or for non-invasive active devices.
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 containing medicinal substances, nanomaterials, blood derivatives, spinal implants, joint prostheses, software, devices intended to administer medicines.
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. The rules on reusable invasive devices for surgical use led to reclassifications into IIa. Rule 22 on spinal implants can lead to a class III for devices previously in IIb.
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