Why Your Clinical Investigation Protocol Gets Rejected
I’ve reviewed clinical investigation protocols that took months to write, involved multiple stakeholders, and passed internal approval processes. Then they reach the ethics committee or Notified Body, and the rejection comes back within days. The reason is almost always the same: the protocol wasn’t designed with MDR requirements in mind from the start.
In This Article
Most manufacturers treat the clinical investigation protocol as a clinical document. It’s written by clinical teams, reviewed by medical advisors, and structured like a traditional clinical trial protocol. This approach worked under the old directives.
Under MDR, the protocol must serve a regulatory function first. It’s not just a study design document. It’s the foundation of your clinical evidence strategy, your risk management linkage, and your post-market surveillance plan. If these connections are missing or superficial, the protocol fails before the first patient is enrolled.
The Regulatory Function of the Protocol
Article 62 of MDR 2017/745 sets out requirements for clinical investigations. Article 82 establishes obligations for the sponsor. Together, they create a framework where the protocol must demonstrate regulatory understanding, not just clinical competence.
The protocol must show how the investigation addresses specific gaps in clinical evidence. These gaps should come directly from your clinical evaluation. If your CER identified insufficient data on a particular patient population or use condition, the protocol must target exactly that gap.
I see protocols that propose broad exploratory studies. They aim to generate general safety and performance data. But when the ethics committee or Notified Body reviews the clinical evaluation in parallel, they find no clear link between the investigation objectives and the documented evidence gaps.
The investigation objectives are written generically: “To demonstrate safety and performance of the device.” But the CER shows specific uncertainties about long-term outcomes in diabetic patients. The protocol never mentions this population. The link is broken.
The protocol must also demonstrate how it fits within your overall clinical evidence plan. If you’re relying on equivalence for some claims and clinical investigation for others, the protocol must clarify exactly which claims the investigation will support. This distinction is often missing.
Risk Management Integration
One of the most frequent disconnects I see is between the protocol and the risk management file. Annex XIV of MDR requires that clinical investigations address residual risks. But many protocols never reference the risk analysis.
The protocol should identify which residual risks the investigation will evaluate. It should define endpoints and measurements that directly assess these risks. If your risk file identifies potential tissue damage as a residual risk, the protocol must include specific endpoints to monitor and quantify this risk.
This isn’t about copying risk descriptions into the protocol. It’s about showing a logical chain: the risk exists, current data cannot fully characterize it, and the investigation is designed to generate the missing evidence.
When this chain is absent, reviewers question whether the sponsor understands their own risk profile. And they reject the protocol until the connection is made explicit.
Map each primary and secondary endpoint back to a specific residual risk or evidence gap documented in your technical file. If you cannot draw this line, the endpoint is likely unnecessary or the protocol is addressing the wrong question.
Defining the Study Population
The inclusion and exclusion criteria often fail because they’re copied from similar studies or written too broadly. Under MDR, the study population must reflect the intended use and intended patient population defined in your IFU.
If your device is indicated for adults with moderate to severe disease, but your protocol includes mild cases, the data won’t support your labeling. If your IFU allows use in patients with comorbidities, but your protocol excludes them, you’re generating evidence for a narrower population than you intend to market to.
This mismatch creates a gap between claimed performance and demonstrated performance. Notified Bodies will identify this during review. Ethics committees will question whether the investigation truly serves the regulatory purpose stated in the application.
I’ve seen manufacturers try to justify broad exclusion criteria by citing safety concerns. But if the safety concern is real and clinically relevant, it should be reflected in the IFU as a contraindication or warning. If it’s not clinically significant, it shouldn’t narrow your study population.
Endpoints and Success Criteria
This is where many protocols collapse under scrutiny. The endpoints are described, but the success criteria are vague or absent. The protocol states that safety will be monitored through adverse event reporting. But it never defines what rate of adverse events would be acceptable or unacceptable.
MDR and MDCG 2020-6 emphasize that the investigation must generate sufficient clinical evidence to support the claims. Sufficient means quantifiable. It means defining in advance what results would demonstrate acceptable safety and performance.
Without pre-defined success criteria, the investigation becomes a data collection exercise. Any result can be interpreted favorably. This defeats the purpose of conducting a prospective study.
The success criteria must be justified. If you define a threshold for a complication rate, explain why that threshold is clinically acceptable. Reference published data, clinical guidelines, or accepted benchmarks. Show that your criteria are grounded in medical reality, not commercial optimism.
The protocol states: “Safety will be demonstrated by acceptable rates of adverse events.” But “acceptable” is never defined numerically. The protocol provides no comparison to existing treatments or objective benchmark. Reviewers will ask: acceptable to whom, based on what standard?
Statistical Considerations
Many protocols include a sample size calculation, but the calculation isn’t linked to the clinical question. The sample size is powered to detect a difference that isn’t relevant to the regulatory claim, or it’s based on assumptions that aren’t documented or justified.
The statistical section must show how the sample size was determined based on the primary endpoint, the expected effect size, and the level of certainty required. If the study is a single-arm design, the justification for not including a control group must be clear and defensible.
For non-inferiority or equivalence designs, the choice of margin must be explained. Why is this margin clinically acceptable? What would happen if the device performs at the margin? Is that outcome still beneficial for patients?
I’ve reviewed protocols where the non-inferiority margin was set at 10%, but no rationale was provided. When questioned, the sponsor explained it was based on feasibility, not clinical reasoning. That’s not acceptable under MDR. The margin must reflect medical judgment, not logistical convenience.
Data Management and Quality
The protocol must describe how data will be collected, recorded, and verified. This isn’t a formality. Under Article 62, the sponsor must ensure data quality and integrity. The protocol must outline the systems and processes that will achieve this.
If you’re using an electronic data capture system, describe it. If you’re planning on-site monitoring visits, define the frequency and scope. If you’re relying on source document verification, explain how that will be conducted.
When these details are missing, ethics committees question whether the sponsor has the infrastructure to conduct a compliant investigation. And Notified Bodies question whether the resulting data will be reliable enough to support regulatory claims.
Post-Market Linkage
The protocol should explain how the investigation feeds into your post-market clinical follow-up. If you’re conducting a pre-market investigation, will the same endpoints be monitored post-market? Will the same patient population be tracked?
This continuity is important. MDCG 2020-7 on post-market clinical follow-up emphasizes that PMCF should build on pre-market data. If your investigation uses endpoints that won’t be feasible to monitor post-market, you’re creating a discontinuity in your evidence stream.
The protocol should also address how you’ll handle findings that emerge during the investigation. If a safety signal appears, what is your process for assessing it, reporting it, and potentially modifying the device or the investigation?
These aren’t hypothetical questions. They reflect the reality that clinical investigations rarely go exactly as planned. Your protocol must show that you’ve thought through the contingencies.
Write the PMCF plan first, then design the clinical investigation protocol to align with it. This ensures continuity in your clinical evidence strategy and makes both documents stronger.
Writing for the Reviewer
The protocol will be reviewed by people who read dozens of protocols each month. They know what a well-constructed protocol looks like. They know when corners have been cut or when regulatory requirements have been addressed superficially.
Write the protocol assuming the reviewer will cross-reference it against your CER, your risk management file, and your IFU. Because they will. Any inconsistency will be identified and will result in questions or rejections.
Use clear section headings that map to regulatory requirements. Make it easy for the reviewer to find where you’ve addressed each MDR obligation. Don’t make them search through dense paragraphs to determine whether you’ve met the standard.
And don’t over-complicate the language. Regulatory reviewers value clarity and precision. If you can explain your design in straightforward terms, do so. Complexity for its own sake raises suspicion that you’re trying to obscure weaknesses.
Final Considerations
Before you submit the protocol, conduct an internal review that simulates the external review process. Have someone who wasn’t involved in writing the protocol read it critically. Ask them to identify gaps, ambiguities, or unsupported claims.
Check that every objective maps to an endpoint, every endpoint maps to a success criterion, and every success criterion is justified. Check that the study population matches the intended use. Check that the risk management linkage is explicit.
These checks take time. But they prevent the much longer delays that come from rejections and resubmissions.
The clinical investigation protocol is not a standalone document. It’s part of a regulatory system. When it’s designed with that system in mind, it becomes a tool that accelerates approval rather than a barrier that delays it.
Peace,
Hatem
Clinical Evaluation Expert for Medical Devices
Follow me for more insights and practical advice.
Frequently Asked Questions
What is a Clinical Evaluation Report (CER)?
A CER is a mandatory document under MDR 2017/745 that demonstrates the safety and performance of a medical device through systematic analysis of clinical data. It must be updated throughout the device lifecycle based on PMCF findings.
How often should the CER be updated?
The CER should be updated whenever significant new clinical data becomes available, after PMCF activities, when there are changes to the device or intended purpose, and at minimum during annual reviews as part of post-market surveillance.
What causes CER rejection by Notified Bodies?
Common reasons include inadequate equivalence demonstration, insufficient clinical data for claims, poorly structured SOTA analysis, missing gap analysis, and lack of clear benefit-risk determination. Structure and logical flow are as important as the data itself.
Which MDCG guidance documents are most relevant for clinical evaluation?
Key documents include MDCG 2020-5 (Equivalence), MDCG 2020-6 (Sufficient Clinical Evidence), MDCG 2020-13 (CEAR Template), MDCG 2020-7 (PMCF Plan), and MDCG 2020-8 (PMCF Evaluation Report).
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Peace, Hatem
Your Clinical Evaluation Partner
Follow me for more insights and practical advice.
– MDR 2017/745 Article 62 (Clinical investigations)
– MDR 2017/745 Article 82 (Obligations of sponsors)
– MDR 2017/745 Annex XIV (Clinical evaluation and post-market clinical follow-up)
– MDCG 2020-6 (Sufficient clinical evidence)
– MDCG 2020-7 (Post-market clinical follow-up)
