Your equivalence claim just became your biggest liability

Written by HATEM RABEH, MD, MSc Ing

Your Clinical Evaluation Expert And Partner

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When you transition a legacy device from MDD to MDR, you’re not just updating paperwork. You’re rebuilding the clinical foundation under regulatory scrutiny that didn’t exist before.

The MDD allowed manufacturers to demonstrate safety and performance through equivalence with minimal clinical data. Many devices reached the market with CERs that were essentially comparative tables and literature summaries. Under MDR Article 61 and Annex XIV, that approach is no longer sufficient.

What worked for your technical file in 2016 will fail review in 2024. Not because the device changed, but because the regulatory expectations fundamentally shifted.

The Illusion of Equivalence

Most legacy devices rely on equivalence claims. The clinical evaluation was built around showing that your device is similar enough to a predicate device with established clinical performance.

Under MDD, equivalence requirements were loosely defined. Manufacturers had significant flexibility in how they justified similarity. If the predicate was on the market and no major safety signals existed, the equivalence claim usually held.

MDR changed the entire framework.

MDCG 2020-6 introduced strict criteria for demonstrating equivalence. The guidance defines equivalence as devices being “essentially the same” in clinical, technical, and biological characteristics. Not similar. Not comparable. Essentially the same.

When you transition your legacy device, the Notified Body will apply these stricter criteria to an equivalence claim that was accepted under the old rules. This creates a structural gap.

Your original equivalence justification may have been adequate in 2015. It is almost certainly inadequate now.

Where the Gaps Appear During Review

Let me walk you through the most common deficiencies I see when legacy CERs enter MDR review.

Gap 1: Technical Comparison Lacks Depth

The technical comparison table in your CER lists device features side by side. Materials, dimensions, operating principles, accessories. Columns marked “equivalent” or “similar.”

Under MDD, this was often sufficient. Under MDR, the Notified Body will challenge every “similar” designation.

What does “similar” mean? How similar? What is the clinical impact of the difference? Why is this difference not clinically significant?

If your device uses a slightly different coating material, a different sterilization method, or operates at a different frequency range, you must justify why these differences do not affect clinical safety and performance.

I’ve seen reviews where a single material difference led to a complete breakdown of the equivalence claim because the manufacturer could not demonstrate that the clinical effect was identical.

Gap 2: Clinical Comparison Assumes Too Much

Your CER claims equivalence based on the same intended use. Same anatomical site, same patient population, same clinical indication.

But when the Notified Body looks closer, the intended use statements are not identical. Your device is indicated for patients with mild to moderate disease. The predicate was validated in a broader population. Your device has a slightly different contraindication list. The instructions for use specify a different procedure duration.

These are not minor administrative differences. They are clinical differences that affect the applicability of the predicate’s clinical data to your device.

MDCG 2020-6 requires equivalence in clinical performance. That means the devices must perform identically in the same clinical context. If the context differs even slightly, the clinical data from the predicate may not fully support your device.

During transition reviews, Notified Bodies are scrutinizing these clinical details far more carefully than they did under MDD. A vague intended use statement or a poorly defined patient population will trigger questions that your CER may not be able to answer.

Gap 3: Biological Comparison Ignored or Underestimated

This is the gap that catches manufacturers by surprise.

Your device and the predicate use the same materials. Stainless steel, silicone, polyethylene. The biological evaluation report from 2014 concluded that both devices are biocompatible according to ISO 10993.

Under MDD, this was usually enough to satisfy the biological comparison for equivalence.

Under MDR, biological equivalence requires more than biocompatibility testing. It requires demonstrating that the materials and their interaction with tissue produce the same biological response.

If the devices have different surface treatments, different manufacturing processes, or different residual chemical profiles, the biological interaction may differ even if both devices pass ISO 10993 testing.

Notified Bodies are now asking: Do you have data showing that the biological response is identical? Not just safe. Identical.

Most legacy CERs do not address this level of detail. The biological evaluation was done separately, and the CER assumed equivalence based on material type alone.

Gap 4: Predicate Device No Longer Supports the Claim

Here’s a scenario that creates serious problems during transition.

Your device was granted a certificate in 2016 based on equivalence to a predicate device that was widely used and had a strong clinical track record.

Now, in 2024, you’re transitioning to MDR. You update the CER, reference the same predicate, and submit for review.

The Notified Body asks: Is the predicate device still on the market? Does it have an MDR certificate? What is the current clinical evidence supporting the predicate?

You discover that the predicate was withdrawn from the market two years ago. Or it failed MDR transition. Or the manufacturer decided not to renew the certificate.

Your equivalence claim is now based on a device that is no longer considered compliant under current regulations. The clinical data supporting that device may still be valid, but the regulatory foundation has disappeared.

MDCG 2020-6 does not explicitly require that the predicate hold an MDR certificate, but Notified Bodies are increasingly cautious about accepting equivalence to devices that are no longer on the market or have not successfully transitioned.

If you cannot demonstrate that the predicate remains a valid benchmark, your equivalence claim weakens significantly.

Gap 5: Literature Search Does Not Cover the Gap

Your CER includes a literature review. The search protocol was defined in 2015 and updated in 2020. You identified clinical studies on the predicate device and other similar devices in the same category.

During MDR review, the Notified Body identifies a gap. The literature supports the general device type, but it does not specifically address the differences between your device and the predicate.

For example, your device has a modified design feature that improves usability. The literature does not cover devices with that specific feature. There are no clinical studies demonstrating that this design modification does not affect clinical outcomes.

The CER concludes that the modification is minor and clinically irrelevant, but there is no data to support that conclusion.

This is a classic gap in legacy CERs. The literature search was designed to support the device category, not to address specific differences that challenge the equivalence claim.

MDCG 2020-6 and MDCG 2021-25 emphasize that the clinical evidence must be sufficient to address all relevant clinical questions. If a design difference raises a clinical question, the literature must answer it or you must generate new data.

Why These Gaps Were Invisible Under MDD

These deficiencies existed in your CER long before MDR came into force. So why are they only surfacing now?

Under MDD, Notified Body reviews were less detailed. The conformity assessment focused on demonstrating that the device met essential requirements. If the equivalence claim was reasonable and the device had no major safety signals, the review moved forward.

MDR introduced a more rigorous conformity assessment. Annex XIV Part A of MDR requires that the CER demonstrate compliance with general safety and performance requirements using clinical evidence. The Notified Body must verify that the evidence is sufficient, and MDCG guidance documents define what “sufficient” means in practice.

Notified Bodies are now required to assess whether the clinical evaluation is adequate according to these stricter criteria. They are held accountable for this assessment by the regulatory authorities that designate them.

This means that assumptions that were accepted under MDD are now challenged. Gaps that were overlooked are now identified as deficiencies.

The device hasn’t changed. The clinical data hasn’t changed. But the regulatory interpretation of what constitutes sufficient evidence has fundamentally shifted.

What Happens When the Gap Is Identified

When a Notified Body identifies a gap during transition review, the process does not simply continue with a minor correction request.

The review is suspended until the gap is addressed. You receive a detailed deficiency letter outlining the specific insufficiencies in the equivalence justification or clinical evidence.

You now have limited options.

You can attempt to strengthen the equivalence claim by providing additional technical, clinical, or biological data that closes the gap. This may involve commissioning new testing, conducting additional literature searches, or obtaining expert opinions.

Or you can abandon the equivalence route and generate new clinical data specific to your device. This means clinical investigations, PMCF studies, or registry data that directly demonstrate the safety and performance of your device without relying on a predicate.

Both options require time, resources, and often result in significant delays to the transition timeline.

I’ve seen transition projects stall for six to twelve months because the manufacturer underestimated the gap and attempted to resolve it with document revisions rather than addressing the underlying evidence deficit.

How to Identify Gaps Before Review

The best time to identify these gaps is before submission, not during Notified Body review.

This requires conducting a critical internal assessment of your equivalence claim using the MDR criteria defined in MDCG 2020-6.

Go through your technical comparison line by line. For every difference, no matter how minor it seems, ask: Can I justify why this difference is clinically irrelevant? Do I have data to support that justification?

Review your clinical comparison. Are the intended use statements truly identical? Are the patient populations identical? Are the contraindications and warnings identical? If not, do I have clinical evidence that covers those differences?

Examine your biological comparison. Do I have evidence that the biological interaction is the same, or am I assuming it based on material type alone?

Verify that your predicate device is still a valid benchmark. Is it on the market? Does it have current regulatory status? Is the clinical data supporting it still considered robust?

Review your literature search. Does it specifically address the differences between my device and the predicate? Are there clinical questions raised by those differences that the literature does not answer?

This assessment is uncomfortable because it often reveals that your equivalence claim is weaker than you believed. But it is far better to discover this internally than to discover it when the Notified Body suspends your review.

The Real Question

The gaps I’ve described are not theoretical. They appear in almost every legacy device transition I review.

The question is not whether your CER has gaps. The question is whether you identify them before the Notified Body does.

Equivalence was a practical regulatory tool under MDD. It allowed devices to reach the market efficiently when clinical data generation was not feasible.

Under MDR, equivalence is still possible, but the bar is significantly higher. The justification must be airtight. The differences must be clinically irrelevant, and you must be able to prove it.

If you cannot meet that standard, your equivalence claim becomes your biggest liability during transition.

In the next part of this series, I’ll walk through what happens when equivalence fails and you need to generate new clinical data under time pressure.

For now, take a close look at your equivalence justification. Because the assumptions you made in 2015 will not survive scrutiny in 2024.

Peace,
Hatem
Clinical Evaluation Expert for Medical Devices
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