Why Most Equivalence Claims Collapse Under Review

Written by HATEM RABEH, MD, MSc Ing

Your Clinical Evaluation Expert And Partner

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Equivalence under MDR is not a similarity judgment. It is a structured demonstration that must satisfy three simultaneous dimensions defined in Article 61(5) and Annex XIV. Clinical, technical, and biological. Miss one dimension, and the entire claim collapses.

The problem is not that manufacturers ignore these dimensions. The problem is that they underestimate what each dimension actually requires.

What Technical Equivalence Actually Means

Technical equivalence is not about listing similar features. It is about proving that two devices share the same intended purpose, function, design, raw materials, and performance characteristics to a degree that justifies using one device’s clinical data to support the other.

MDCG 2020-5 defines this clearly. Yet I see submissions where manufacturers claim equivalence between devices that differ in critical aspects, then argue those differences are “minor” without justification.

A catheter with a different coating material. A screw with modified thread geometry. A sensor using a different detection principle. These are not minor differences if they affect performance or safety.

The first failure point is intended purpose. Many manufacturers claim equivalence between devices that target different patient populations, different anatomical sites, or different stages of disease. The devices may look similar, but if the clinical context differs, the equivalence claim cannot hold.

The second failure point is design and materials. Manufacturers often focus on the overall device architecture and ignore critical details. A coating that reduces friction, a polymer that degrades differently, a metal alloy with different mechanical properties—these are not cosmetic changes. They affect how the device interacts with tissue.

The third failure point is performance specifications. I see tables comparing devices where key parameters are missing or where ranges overlap partially but not completely. Reviewers notice this immediately.

The Biological Equivalence Gap

Biological equivalence is where most arguments fail.

Manufacturers often treat biological equivalence as a checkbox. Same body contact type. Same duration of contact. Same tissue interaction category. But biological equivalence is not about ISO 10993 categories. It is about actual biological interaction.

A device that contacts blood for less than 24 hours and a device that contacts blood for more than 30 days are not biologically equivalent, even if both are vascular implants. The immune response is different. The thrombogenicity profile is different. The risk of infection is different.

Material composition matters more than manufacturers want to admit. A device made from one type of stainless steel is not automatically equivalent to a device made from another type, even if both meet general biocompatibility requirements. Corrosion behavior differs. Ion release profiles differ. Long-term tissue response differs.

Surface treatments create another layer of complexity. A polished surface and a textured surface do not interact with tissue in the same way. A hydrophilic coating and a hydrophobic coating do not behave identically in contact with blood or mucosa.

Reviewers look for direct evidence that the biological interaction is equivalent, not assumptions based on broad categories.

What Clinical Equivalence Requires

Clinical equivalence is the third dimension, and it ties the other two together.

Here, manufacturers must demonstrate that any technical or biological differences do not produce different clinical outcomes. This is not a theoretical argument. It requires data.

I see clinical evaluation reports where the equivalent device has data from a different patient population, different clinical settings, or different follow-up durations, yet the manufacturer claims the data is transferable. Reviewers do not accept this.

If your device is used in outpatient settings and the equivalent device was studied in hospital settings, the clinical context is not the same. If your device targets elderly patients and the equivalent device was tested in younger populations, the risk profile is not the same.

Clinical equivalence also requires that the equivalent device has sufficient clinical data in the first place. If the equivalent device itself lacks robust data, you cannot build your clinical evaluation on a weak foundation.

The weakest equivalence claims I review are those where the manufacturer lists a few similarities, adds a comparison table, and assumes equivalence is demonstrated. This is not a demonstration. It is a summary.

A proper equivalence demonstration includes detailed side-by-side analysis, direct comparison of all relevant characteristics, explicit justification for any differences, and clear explanation of why those differences do not affect clinical safety or performance.

When Equivalence Is Not Possible

Not every device can be supported through equivalence. Some devices require their own clinical data because the differences are too significant or the available data is insufficient.

New materials, new mechanisms of action, new patient populations, new implant durations—these often break equivalence. Manufacturers resist this because generating new clinical data is expensive and time-consuming. But attempting to force an equivalence claim where it does not fit creates more problems.

I see this most often with incremental design changes. A manufacturer modifies a device slightly, calls it equivalent to the previous version, and tries to rely on old data. But even small changes can affect performance. A slightly different drug release profile, a modified delivery mechanism, a new size or configuration—these can shift the risk-benefit balance.

Reviewers increasingly challenge these claims. They expect manufacturers to either demonstrate equivalence rigorously or acknowledge that new clinical data is needed. There is no third option.

How Notified Bodies Evaluate Equivalence

Notified Bodies approach equivalence with skepticism. They assume the claim is invalid until proven otherwise.

They start by checking if the equivalent device is clearly identified. Name, manufacturer, UDI if available, regulatory status. If this is vague, the review stops immediately.

Then they assess the three dimensions systematically. They look for gaps in the comparison, unexplained differences, and missing justifications. They expect every characteristic to be addressed, not just the obvious ones.

They pay attention to the clinical data from the equivalent device. Is it recent? Is it robust? Is it applicable to the subject device? If the equivalent device is old or has limited data, the equivalence claim weakens.

They also check if the equivalent device itself relied on equivalence. If your device claims equivalence to a device that also relied on equivalence, the chain must be traceable and valid. Notified Bodies do not accept long equivalence chains without clear justification.

When equivalence is rejected, manufacturers often respond by adding more comparison tables or more text. This rarely solves the problem. The issue is not the amount of information. It is the logic and evidence behind the claim.

What a Solid Equivalence Demonstration Looks Like

A solid equivalence demonstration starts with a clear statement of why equivalence is being claimed and what it supports. Is it a full clinical evaluation or a supplementary strategy? Is it for a new device or a device modification?

Then it provides a detailed technical comparison. Every aspect that could affect safety or performance is listed, compared, and justified. Materials, design features, manufacturing processes, performance specifications, intended use, patient population, clinical settings.

Differences are not ignored or downplayed. They are addressed directly. If a difference exists, the manufacturer explains why it does not affect clinical outcomes. This requires reasoning, not assertion.

Biological equivalence is demonstrated with evidence. Biocompatibility data, tissue interaction studies, degradation profiles, immune response data. Not assumptions.

Clinical equivalence is supported with applicable data. The equivalent device has robust clinical evidence. The clinical context matches. The patient population is comparable. The follow-up duration is sufficient.

Finally, the demonstration includes a clear conclusion. Either equivalence is established, and the clinical data from the equivalent device can be used, or equivalence is not established, and additional data is needed.

This explicit conclusion is what reviewers need. Without it, they must interpret the data themselves, and their interpretation may not align with the manufacturer’s intent.

Why Equivalence Keeps Failing

Equivalence fails because manufacturers treat it as a shortcut rather than a rigorous demonstration.

They want to avoid generating new clinical data, so they stretch equivalence to cover devices that are only superficially similar. They focus on similarities and minimize differences. They use vague language and incomplete comparisons.

But equivalence is not a loophole. It is a legitimate strategy when the conditions are met. When the devices are truly equivalent, when the data from the equivalent device is robust and applicable, when the demonstration is thorough and transparent.

Reviewers recognize the difference immediately. A genuine equivalence demonstration is detailed, honest about differences, and clear in its conclusions. A forced equivalence claim is vague, dismissive of differences, and lacks logical structure.

Most rejected equivalence claims fall into the second category. The devices were not equivalent, but the manufacturer tried to make them appear equivalent through incomplete analysis.

What This Means for Your Clinical Evaluation Strategy

If you are planning to use equivalence, start by asking whether it is genuinely applicable. Not whether it would be convenient, but whether the devices meet the three-dimensional requirement.

If they do, build the demonstration carefully. Address every dimension. Provide evidence. Justify differences. Be explicit in your conclusions.

If they do not, do not force it. Acknowledge that new clinical data is needed and plan accordingly. A weak equivalence claim that gets rejected wastes more time than generating the data from the start.

Notified Bodies are not trying to make life difficult. They are applying the regulation as written. Equivalence is allowed, but it must be demonstrated, not assumed.

The devices you thought were equivalent may not be. The data you thought was transferable may not be. The differences you thought were minor may be critical. Recognizing this early prevents far larger problems later.

Peace,
Hatem
Clinical Evaluation Expert for Medical Devices
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