When Your Clinical Data Breaks Your Equivalence Claim

Written by HATEM RABEH, MD, MSc Ing

Your Clinical Evaluation Expert And Partner

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This is not a theoretical problem. It happens more often than manufacturers expect, and when it does, it triggers one of the most uncomfortable regulatory conversations you can have.

Because the question from the Notified Body is simple: if your own data contradicts the equivalence you claimed, was the equivalence ever valid?

The Regulatory Foundation That Gets Tested

Under MDR Article 61(5) and Annex XIV Part A, you can rely on equivalence to demonstrate conformity when your device is equivalent to another device for which clinical data exists. The MDCG 2020-5 guidance sets the framework: technical, biological, and clinical equivalence must all be justified.

That equivalence claim sits at the foundation of your clinical evaluation. Your GSPR conformity depends on it. Your benefit-risk conclusion depends on it. Your entire clinical strategy depends on it.

And then your clinical investigation produces data that does not align.

This is where many manufacturers misunderstand the situation. They think the issue is about updating the CER with new data. They think it is a documentation problem.

It is not. It is a validity problem.

What Contradiction Actually Means

Let me be precise about what I mean by contradiction, because this word carries weight in a regulatory file.

Contradiction does not mean your device is unsafe. It does not mean your investigation failed. It means your clinical investigation data shows a difference from the equivalent device that challenges one of the three equivalence pillars.

Maybe the performance is different. Not worse, but different.

Maybe the safety profile is similar overall, but a specific adverse event occurs at a different rate.

Maybe the clinical benefit manifests differently across patient subgroups than it did for the equivalent device.

These are not catastrophic findings. But they are material differences, and material differences undermine equivalence.

Why This Exposes a Deeper Problem

When clinical investigation data contradicts equivalence, the Notified Body is not just questioning the new data. They are questioning the original equivalence justification.

Because if your device behaves differently in a clinical investigation, one of two things must be true:

Either the equivalence claim was not as solid as you thought, or the clinical investigation design did not properly reflect the intended use and patient population of the equivalent device.

Both are serious problems.

If the equivalence was weak, then your entire clinical evaluation may have been built on insufficient justification. The literature you relied on, the gaps you accepted, the benefit-risk balance you concluded—all of it rested on an equivalence that your own data now challenges.

If the investigation design was the issue, then you ran a study that does not answer the questions it was supposed to answer. That raises questions about your clinical development strategy and your understanding of your own device.

Neither explanation satisfies a Notified Body.

The Immediate Regulatory Consequences

Let me walk through what happens next, because the sequence matters.

First, the Notified Body will issue a finding. It will reference the contradiction and request justification. They will ask you to clarify whether the equivalence claim remains valid in light of the new data.

This is not a minor clarification request. It is a fundamental question about the validity of your clinical evidence base.

If you cannot demonstrate that the equivalence remains valid, you have three options, and none of them are simple.

Option 1: Revise the equivalence claim.

You narrow the scope of equivalence. You state that equivalence applies only to certain aspects of the device, or only in certain populations, or only for certain endpoints.

This sounds reasonable, but it has cascading effects. Every section of your CER that relied on the broader equivalence must now be re-justified with additional data. If you no longer claim full equivalence, you must fill those gaps with your own clinical evidence.

That means your clinical investigation is no longer supplementary. It is now primary evidence. And you need to ensure it is sufficient to support conformity on its own.

Option 2: Demonstrate that the difference is not material.

You provide a detailed scientific justification showing that the observed difference does not affect the clinical equivalence pillars. This requires statistical analysis, clinical reasoning, and often additional literature to contextualize the finding.

This works only if the difference is genuinely minor and does not affect safety or performance in a way that matters to patients or users. If the Notified Body disagrees with your assessment of materiality, you are back to Option 1.

Option 3: Withdraw the equivalence claim entirely.

You treat your device as non-equivalent and rely solely on your own clinical data. This is the cleanest path technically, but it requires sufficient clinical evidence to stand alone.

If your clinical investigation was designed as supplementary evidence—small sample size, limited follow-up, narrow endpoints—it will not be sufficient. You will need additional studies, which means delays, costs, and potential gaps in your evidence base during the transition.

What Should Have Happened Earlier

This situation is almost always preventable, but prevention requires honesty during equivalence justification.

Before you commit to an equivalence claim, you need to ask whether your clinical investigation could produce data that contradicts it. If yes, you need to plan for that scenario before you submit your CER.

That means designing your investigation to either confirm equivalence directly or to provide sufficient standalone evidence if equivalence cannot be confirmed.

It also means being conservative in your equivalence claim. If there is any uncertainty about technical, biological, or clinical equivalence, do not claim full equivalence. Claim partial equivalence and design your clinical program to fill the gaps.

I see manufacturers do the opposite. They claim broad equivalence to minimize their clinical evidence burden, then run a small investigation as a formality. When that investigation shows a difference, they have no fallback plan.

The regulatory path forward becomes a reactive scramble instead of an executed strategy.

How Notified Bodies Actually Evaluate This

Notified Bodies do not approach this issue with flexibility. They approach it with suspicion.

When your own clinical data contradicts your equivalence claim, it signals that you may not have understood your device well enough at the time of the original submission. That makes them question other aspects of your technical documentation and risk management.

They will look at your original equivalence justification with fresh scrutiny. They will ask why the differences were not anticipated. They will question whether your literature search was thorough enough, whether your equivalent device selection was appropriate, whether your risk management considered the possibility of differences.

If the contradiction is significant, they may request a full revision of the CER, not just an addendum. That means re-opening the clinical evaluation, re-analyzing the benefit-risk balance, and potentially delaying certification or surveillance decisions.

This is why I tell manufacturers that equivalence is not a shortcut. It is a commitment. You are committing to a specific technical and clinical profile, and if your device does not match that profile, the commitment breaks.

The Strategic Lesson

If you are planning a clinical investigation for a device that relies on equivalence, you need to be clear about what that investigation is really for.

If it is to confirm equivalence, design it to test the equivalence pillars directly. Measure the same endpoints, use the same population, compare the results explicitly. Make the investigation a validation of the equivalence claim.

If it is to supplement equivalence with device-specific data, make sure the supplementary data cannot contradict the core equivalence justification. Focus on secondary endpoints, subgroup analyses, or long-term follow-up that adds depth without challenging the foundation.

If there is any risk that your device might perform differently, do not rely on equivalence as your primary pathway. Treat the investigation as standalone evidence from the beginning and design it accordingly.

The worst strategy is to claim equivalence, run a small supplementary study, and hope the data aligns. Hope is not a clinical strategy, and it is definitely not a regulatory strategy.

Final Consideration

When clinical investigation data contradicts your equivalence claim, you are not just dealing with a technical issue. You are dealing with a credibility issue.

Notified Bodies, competent authorities, and auditors will ask how this happened. They will ask why the difference was not anticipated. They will ask whether your clinical evaluation process is robust enough to identify these risks before they become regulatory problems.

The answer to those questions determines not just the resolution of this specific issue, but the level of scrutiny your entire clinical program will face going forward.

That is the real consequence of contradictory data. It is not just what it says about your device. It is what it says about your process.

Peace,
Hatem
Clinical Evaluation Expert for Medical Devices
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