Sterilization changes everything. Does your CER reflect this?

Written by HATEM RABEH, MD, MSc Ing

Your Clinical Evaluation Expert And Partner

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This happens more often than you think. Manufacturers develop a non-sterile device, gather clinical data, write the clinical evaluation report, and then decide to introduce a sterile version. They assume the clinical evaluation can simply carry over with minimal adjustment.

It cannot.

The regulatory logic behind this is straightforward but often misunderstood. When you introduce sterilization, you are not just adding a process step. You are changing the risk profile, the performance characteristics, and the clinical context of the device. The MDR does not allow you to ignore this.

Why Sterilization Is Not Just a Process Addition

Sterilization affects the device at multiple levels. It impacts material integrity, introduces potential residuals, and alters the interaction between the device and tissue. These are not theoretical concerns. They are documented sources of clinical risk.

Ethylene oxide can leave residuals that cause hypersensitivity reactions. Gamma irradiation can degrade polymers and change mechanical properties. Steam sterilization can affect surface characteristics and corrosion resistance. Each method carries specific risks that must be evaluated clinically.

But there is another dimension that manufacturers often overlook. The sterile variant is used in a different clinical context. A non-sterile device may be cleaned and sterilized by the hospital before use. A sterile device arrives ready for immediate use in the operating room. This changes the handling, the timing, the infection control assumptions, and the overall risk-benefit analysis.

What the MDR Requires

MDR Article 61 requires that the clinical evaluation address all intended purposes and all configurations of the device. A sterile variant is a different configuration. Annex XIV specifies that the clinical evaluation must cover the specific characteristics of the device, including sterilization method and any residuals.

MDCG 2020-5 on clinical evaluation clarifies that equivalence claims must account for technical, biological, and clinical characteristics. Sterilization affects all three. If your predicate device was non-sterile and your subject device is sterile, the equivalence pathway becomes significantly more complex. In many cases, it is no longer valid.

The regulation does not say you must conduct a new clinical investigation for every sterile variant. But it does say you must justify why the existing clinical data remains applicable. That justification must be thorough, specific, and supported by evidence.

Most manufacturers fail here because they treat the justification as a formality. They write a paragraph stating that sterilization does not affect safety or performance. They provide no verification data. No biocompatibility testing post-sterilization. No analysis of how the sterilization method interacts with the device material. The Notified Body sees this immediately.

The Clinical Evaluation Structure for Sterile Variants

If you are introducing a sterile variant of an existing non-sterile device, your clinical evaluation must include several specific elements.

First, you must demonstrate that the sterilization process does not negatively affect device performance. This requires verification testing after sterilization. Mechanical properties, dimensional stability, surface characteristics, and any functional parameters must be tested on sterilized samples. This data must be referenced in the clinical evaluation report.

Second, you must address biocompatibility in the sterilized state. ISO 10993 testing conducted on non-sterilized samples is not sufficient. Sterilization can introduce extractables, change surface chemistry, and alter cytotoxicity profiles. You need post-sterilization biocompatibility testing or a robust justification for why it is not needed.

Third, you must evaluate sterilization residuals. If you use ethylene oxide, you must demonstrate that residual EtO and ethylene chlorohydrin levels are below acceptable thresholds. If you use gamma irradiation, you must assess degradation products. This is not just a technical file requirement. It is a clinical safety question that belongs in the CER.

Fourth, you must address the clinical context. A sterile device is used differently than a non-sterile device. It may be used in more acute settings, with less preparation time, or by different users. The risk-benefit analysis must reflect this. The state of the art review must include literature on infection control, sterile packaging integrity, and any complications related to sterilization failures.

When Equivalence Becomes Questionable

Many manufacturers attempt to use equivalence to bridge clinical data from a non-sterile predicate to a sterile subject device. This approach works only under very specific conditions.

The equivalence claim must show that the devices are equivalent in technical, biological, and clinical characteristics. Sterilization affects biological characteristics directly. If the predicate was non-sterile and intended for hospital sterilization, and your device is pre-sterilized, the biological interaction is different. The sterilization method you use may introduce residuals or material changes that the predicate does not have.

You can still claim equivalence if you demonstrate that these differences do not affect clinical safety and performance. But this requires data. Comparative biocompatibility testing. Comparative material analysis. Literature supporting the clinical safety of your sterilization method for this device type.

In many cases, I see manufacturers reference a predicate device from another manufacturer that is also sterile but uses a different sterilization method. They assume this resolves the issue. It does not. Ethylene oxide and gamma irradiation are not interchangeable from a clinical evaluation perspective. Each method has different residual risks and different effects on materials.

The Notified Body will ask: Why do you believe the clinical data from a device sterilized with gamma irradiation applies to your device sterilized with ethylene oxide? If you cannot answer this with evidence, the equivalence claim fails.

The PMCF Implications

Post-market clinical follow-up must also account for the sterile variant. If you are relying on PMCF data from a non-sterile version to support a sterile version, you must justify why that data remains relevant.

In practice, this means your PMCF plan should include specific provisions for monitoring sterilization-related adverse events. Hypersensitivity reactions. Infections that could indicate sterility failure. Any complications that could be linked to residuals or material degradation.

If you introduce a sterile variant after years of marketing a non-sterile version, the PMCF plan must be updated. The periodic safety update report must address both variants separately or provide a clear rationale for pooled analysis. This is not optional. It is an MDR requirement under Article 86 and Annex XIV.

What Happens in Real Audits

I have been in audit rooms where the Notified Body focused the entire clinical evaluation discussion on the sterilization issue. They asked for the biocompatibility test reports. They asked whether the tests were conducted on sterilized samples. They asked how the manufacturer determined the clinical relevance of sterilization residuals.

In one case, the manufacturer had submitted ISO 10993 testing conducted on raw material samples before sterilization. The Notified Body rejected the data. The reasoning was simple: the clinical risk is not from the raw material. It is from the material as it contacts the patient, which includes any changes introduced by sterilization.

The manufacturer had to repeat the entire biocompatibility testing program on sterilized samples and update the clinical evaluation report. The delay was six months.

In another case, the manufacturer used equivalence to a predicate device that was sterilized using a different method. The Notified Body asked for a comparative analysis of the two sterilization methods and their clinical implications. The manufacturer did not have this analysis. The equivalence claim was rejected, and the manufacturer had to conduct a literature review on the clinical safety of their specific sterilization method.

These are not edge cases. They are predictable outcomes when the clinical evaluation does not address sterilization with the rigor the MDR requires.

Practical Guidance

If you are preparing a clinical evaluation for a sterile device variant, start by treating it as a new device configuration. This does not mean you need new clinical data, but it does mean you need to justify why the existing data applies.

Include a dedicated section in the CER on sterilization. Address the method, the validation, the impact on materials and biocompatibility, the residual risk, and the clinical context. Reference the verification testing conducted on sterilized samples. Reference the biocompatibility testing post-sterilization. Reference the state of the art literature on your sterilization method.

If you are using equivalence, ensure the predicate device was sterilized using the same method or provide a detailed justification for why a different method does not affect clinical safety. Do not assume the Notified Body will accept general statements.

Update your PMCF plan to monitor sterilization-related risks. If you are marketing both sterile and non-sterile variants, ensure your PMCF data collection distinguishes between them or provide a rationale for combined analysis.

Why This Matters

The distinction between sterile and non-sterile variants is not bureaucratic complexity. It reflects a real difference in clinical risk. Patients are exposed to sterilization residuals. Materials behave differently after sterilization. The clinical context changes.

The MDR requires that the clinical evaluation reflect the device as it is placed on the market. If it is placed on the market sterile, the clinical evaluation must address sterilization comprehensively. If it is not, you are not meeting the regulation.

This issue becomes particularly important during audits, major changes, and new submissions. Notified Bodies are trained to look for gaps between the device description and the clinical evaluation. Sterilization is one of the most common gaps.

Addressing it properly does not require extensive new clinical investigations in most cases. It requires structured thinking, appropriate verification and validation data, and a clinical evaluation report that clearly explains how sterilization affects safety and performance.

If you treat sterilization as a detail, the Notified Body will treat your submission as incomplete. If you address it systematically, you avoid delays and demonstrate regulatory competence.

The question is not whether sterilization matters. It does. The question is whether your clinical evaluation reflects this reality.

Peace,
Hatem
Clinical Evaluation Expert for Medical Devices
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