BOX S-1
The Three Device Classes

•    Class I devices are those for which the general regulatory controls should be sufficient to provide reasonable assurance of safety and effectiveness. Class I may also include any device on which there is insufficient information to judge the adequacy of the controls but that is not represented to be for use in supporting or sustaining human life (or preventing impairment to health) and does not present an unreasonable risk of illness or injury.

•    Class II devices are those that cannot be classified into Class I, because general controls are not sufficient by themselves to provide reasonable assurance of safety and effectiveness, but on which there is sufficient information to establish a special control to provide reasonable assurance. Originally, Class II called solely for performance standards. A performance standard might include provisions regarding the construction, components, ingredients, and properties of the device and its comparability with power systems; provisions for the testing of the device to ensure conformity to the standard; provisions for measurement of performance characteristics of the device; provisions making the device a “restricted device”; and special labeling requirements related to the installation, maintenance, operation, and use of the device. Since 1990, Class II devices have been subject to special controls, which may include performance standards, guidelines for the submission of clinical data in premarket notification submissions in accordance with Section 510(k), and other controls, such as compliance with an FDA guidance document.

•    Class III devices are those that are represented for use in supporting or sustaining life (or preventing impairment of health) or create a potentially unreasonable risk of illness or injury, but which cannot be classified into Class I or Class II, because the general controls are inadequate to give reasonable assurance of safety and effectiveness and the available information is insufficient to establish a special control to provide the requisite assurance.

The Safe Medical Devices Act (SMDA) of 1990 permitted substantial equivalence to be established to marketed postamendment, in addition to preamendment, “predicate” devices, except for devices approved by PMA. Congress’s interpretation of substantial equivalence, as stated in the SMDA, is shown in Box S-2. The SMDA also gave the FDA authority to impose



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