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    Substantial Equivalence

    The legal standard a 510(k) device must meet versus a predicate.

    Reviewed by Christian Espinosa, Founder, Blue Goat CyberLast reviewed May 5, 2026

    Definition

    A device is substantially equivalent if it has the same intended use as the predicate and either the same technological characteristics, or different technological characteristics that do not raise different questions of safety and effectiveness, with performance data demonstrating equivalent safety and effectiveness.
    What the regulation says
    The FDA defines substantial equivalence in 21 CFR 807.100. This is the primary criterion for clearing medical devices through the 510(k) premarket notification pathway. Manufacturers must demonstrate that their new device is as safe and effective as a legally marketed predicate device, as outlined in FDA guidance documents on the 510(k) program.

    What this means in practice

    Substantial equivalence is the legal foundation of the 510(k) pathway. FDA decisions hinge on careful predicate selection and side-by-side comparisons of indications, technology, and performance.

    Examples

    • A manufacturer submits a 510(k) for a new surgical instrument, demonstrating its substantial equivalence to an existing, legally marketed surgical instrument by comparing materials, dimensions, and sterilization methods.
    • A company develops a new in vitro diagnostic device and compares its performance characteristics, such as sensitivity and specificity, to a predicate device already cleared for the same intended use.
    • A medical device company adds a new feature to an existing cleared device and provides data to show that this change does not raise new questions of safety or effectiveness, thus maintaining substantial equivalence to its own predicate device.
    Common pitfalls
    • •Failing to select an appropriate predicate device can lead to significant delays or rejection of a 510(k) submission.
    • •Claiming substantial equivalence without robust side-by-side comparison data will result in FDA deficiencies.
    • •Assuming that minor technological differences will automatically be considered substantially equivalent without justification is a common mistake.
    • •Not adequately addressing new questions of safety and effectiveness raised by technological differences will prevent 510(k) clearance.

    Frequently asked questions

    A predicate device is a legally marketed device to which a new device is compared to establish substantial equivalence. It must be a device that was cleared through the 510(k) process, preamendment, or reclassified.

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    Primary references

    3 sources
    Link health: 3 verified· last checked 2026-06-20
    FDA·1European Commission·1IMDRF·1
    1. 1
      The 510(k) Program Guidance
      Verified
      FDAfda.gov
    2. 2
      European Commission - Medical Devices
      Verified
      European Commissionhealth.ec.europa.eu
    3. 3
      IMDRF Documents
      Verified
      IMDRFimdrf.org

    Inline markers like [1] jump to the matching reference above.