Medical Devices: Definition, Classification, and Regulatory Implications

Abstract

We propose the following definition of a medical device: “A contrivance designed and manufactured for use in healthcare, and not solely medicinal or nutritional.” Current regulatory classifications of medical devices are complex and designed primarily for regulators. We propose a simpler classification, based on (1) the site of application of the device, (2) the time scale of its use, and (3) whether it has an external power source. The regulation of medical devices is less well developed than the regulation of medicinal products, which it could follow more closely. In particular, devices that incorporate medicines should be required to meet the same regulatory standards as medicinal products. This would remove the anomaly that some delivery systems that incorporate medicines are classified as devices while other similar systems that deliver the same medicines are classified as medicinal products. Some improvements might also result from more widespread use of registries, such as those used for prosthetic joint replacements. Registries would allow both a prospective examination of the performance of high-risk devices and a retrospective analysis when signals from other sources of information suggest problems. Those who apply for a marketing authorization for a new device should have to assure regulators of its quality of manufacture, safety, and efficacy before licensing. Even the most straightforward device should be shown to be useable in practice. Trials on patients, or at least simulations of use in the real world, should be practicable for most devices.

Appendices

Appendix 1: European Union regulation of medical devices

The European Union legislation distinguishes four classes (I, IIa, IIb, III) [6]. The class of a device is decided according to rules that consider:

• 1. Duration of use of the device

  • Transient

  • Short-term

  • Long-term

• 2. Invasiveness of the device

  • Non-invasive

  • Invasive

    • Body Orifice

    • Surgically invasive

    • Implantable

The rules also examine whether the device comes into one or more of the following categories:

• 3. Reusable surgical instrument

  “Instrument intended for surgical use by cutting, drilling, sawing, scratching, scraping, clamping, retracting, clipping or similar procedures, without connection to any active medical device and which can be reused after appropriate procedures have been carried out.”

• 4. Active medical device

  “Any medical device operation of which depends on a source of electrical energy or any source of power other than that directly generated by the human body or gravity and which acts by converting this energy.”

• 5. Active therapeutical [sic] device

  “Any active medical device, whether used alone or in combination with other medical devices, to support, modify, replace or restore biological functions or structures with a view to treatment or alleviation of an illness, injury or handicap.”

• 6. Active device for diagnosis

• 7. Central circulatory system

  • Including the pulmonary circulation

• 8. Central nervous system

All medical devices in the European Union must fulfil the essential requirements, which are that “The devices must be designed and manufactured in such a way that, when used under the conditions and for the purposes intended, they will not compromise the clinical condition or the safety of patients, or the safety and health of users or, where applicable, other persons, provided that any risks which may be associated with their use constitute acceptable risks when weighed against the benefits to the patient and are compatible with a high level of protection of health and safety.” Those devices deemed to be in Classes IIa, IIb, and III must fulfil additional requirements. The classification rules are detailed. For example, “Rule 17: All devices manufactured utilizing animal tissues or derivatives rendered non-viable are Class III except where such devices are intended to come into contact with intact skin only.”

There are specific regulations for advanced therapy products that combine a medicine and a device [16].

European standards organizations set out the criteria for a large range of devices, including, for example, the symbols to be used on labels; the form of connectors for liquids and gases; and risk management [17].

Appendix 2: US regulation of medical devices

The US legislation divides medical devices into three classes, intended to reflect the risks that the device poses (Table 3) [18].

Table 3 The US Food and Drug Administration’s classification of medical devices; the full definitions are given in the text

Assignment to one of the three classes is determined by a series of decisions based on the perceived risks of the device when used for its intended purpose [19]. In principle, the least stringent requirements are that the device is perceived to be of low risk, and that the manufacturer has complied with the standards of good manufacturing practices (GMP). A device can be approved through a so-called 510(k) application if it is thought to be “substantially equivalent” to a previously approved device. Any device that is perceived to pose a significant risk and is not similar to a previously approved device may be required to undergo investigation.

The following are the full definitions of the three classes shown in Table 3 [38].

• 1. Class I means the class of devices that are subject to only the general controls authorized by or under sections 501 (adulteration), 502 (misbranding), 510 (registration), 516 (banned devices), 518 (notification and other remedies), 519 (records and reports), and 520 (general provisions) of the act. A device is in class I if (1) general controls are sufficient to provide reasonable assurance of the safety and effectiveness of the device, or (2) there is insufficient information from which to determine that general controls are sufficient to provide reasonable assurance of the safety and effectiveness of the device or to establish special controls to provide such assurance, but the device is not life-supporting or life-sustaining or for a use which is of substantial importance in preventing impairment of human health, and which does not present a potential unreasonable risk of illness of injury.

• 2. Class II means the class of devices that is or eventually will be subject to special controls. A device is in class II if general controls alone are insufficient to provide reasonable assurance of its safety and effectiveness and there is sufficient information to establish special controls, including the promulgation of performance standards, postmarket surveillance, patient registries, development and dissemination of guidance documents (including guidance on the submission of clinical data in premarket notification submissions in accordance with section 510(k) of the act), recommendations, and other appropriate actions as the Commissioner deems necessary to provide such assurance. For a device that is purported or represented to be for use in supporting or sustaining human life, the Commissioner shall examine and identify the special controls, if any, that are necessary to provide adequate assurance of safety and effectiveness and describe how such controls provide such assurance.

• 3. Class III means the class of devices for which premarket approval is or will be required in accordance with section 515 of the act. A device is in class III if insufficient information exists to determine that general controls are sufficient to provide reasonable assurance of its safety and effectiveness or that application of special controls described in paragraph (c)(2) of this section would provide such assurance and if, in addition, the device is life-supporting or life-sustaining, or for a use which is of substantial importance in preventing impairment of human health, or if the device presents a potential unreasonable risk of illness or injury.