CEP vs. CER: What’s the Real Difference?

Ask ten medical device professionals to explain the difference between a CEP and a CER, and you’ll likely get ten different answers. Some use the terms interchangeably. Others treat the CEP as optional. A few have never produced one at all. Under EU MDR, this ambiguity isn’t just a knowledge gap; it’s a compliance risk. Both documents are required, both are reviewed by Notified Bodies, and both serve fundamentally different purposes within your clinical evaluation process.

Let’s set the record straight.

What Is a Clinical Evaluation Plan (CEP)?

The Clinical Evaluation Plan is the strategic document that defines how your clinical evaluation will be conducted. Think of it as the methodology declaration before the evidence is gathered. A well-constructed CEP outlines:

1. The intended purpose and indications for use of the device
2. The clinical claims to be substantiated
3. The criteria for appraising clinical data (inclusion/exclusion criteria)
4. The search strategy for literature identification
5. The approach to demonstrating equivalence, if applicable
6. The reference to applicable standards and regulatory guidance
7. The link between clinical evaluation and risk management activities

The CEP is the “plan”. It must exist before the evaluation begins — not be written retrospectively to justify conclusions already drawn.

What Is a Clinical Evaluation Report (CER)?

The Clinical Evaluation Report is the output of the evaluation process defined in the CEP. It is the documented scientific case for your device’s safety and performance, based on all available clinical data. A complete CER includes:

1. Background on the device, its intended purpose, and the disease/condition it addresses
2. A state of the art analysis
3. Clinical data from literature, clinical investigations, and PMCF
4. Appraisal and analysis of that data
5. Conclusions on safety, performance, clinical benefit, and residual risk
6. Reference to Post-Market Clinical Follow-Up (PMCF) requirements

The CER is the “evidence”. It must follow the methodology set out in the CEP and be updated on a regular basis throughout the device lifecycle.

MDR Requirement: Annex XIV of EU MDR 2017/745 explicitly requires both the CEP and CER as part of the clinical evaluation process. Neither is optional. 

Why the Distinction Matters

1. Notified Bodies Evaluate Both

During conformity assessment, your Notified Body will review the CEP to assess whether your evaluation methodology is scientifically sound — before they even look at your CER conclusions. A weak or absent CEP undermines the credibility of everything that follows.

2. The CEP Protects Your CER from Scope Creep

Without a pre-defined CEP, CER authors often expand or contract their evaluation based on what evidence they find, rather than what the device claims require. This creates a circular argument that reviewers will challenge.

3. Lifecycle Management Is Easier with a Strong CEP

When your device changes, or PMCF data comes in, the CEP provides the baseline against which you update your CER. Without it, every update becomes a document-from-scratch exercise.

A Practical Analogy

Think of the CEP as a clinical trial protocol, and the CER as the clinical study report. You wouldn’t run a clinical trial without a protocol. You wouldn’t submit a study report that doesn’t follow it. The same logic applies here.

Common Mistakes to Avoid

1. Writing the CEP after the CER is complete (this invalidates the methodology)
2. Treating the CEP as a one-page summary rather than a substantive planning document
3. Using the same CEP across multiple device variants without tailoring it
4. Failing to update the CEP when the device’s intended purpose changes
5. Omitting equivalence strategy from the CEP when equivalence will be claimed in the CER

"A strong CEP is a sign of regulatory maturity. It tells a Notified Body that your team understands the science before they evaluate it — not just the documentation".

How They Work Together

The CEP and CER are not independent documents; they are two phases of a single continuous process:

1. Define the scope and methodology (CEP)
2. Gather and appraise the evidence (CER)
3. Update as new data emerges (PMCF → updated CER → revised CEP if needed)

This cycle is ongoing for the life of the device. Manufacturers who manage it systematically maintain a stronger compliance posture and are better positioned during audits and renewals.

Next in the Series

In Blog 3, we go inside the Notified Body review room, sharing the top 5 findings that appear most frequently during CER reviews, and what they reveal about where manufacturers are still falling short.