CER Writing and Literature Review: Common Challenges Affecting Clinical Evaluation Reports Under EU MDR
Literature review forms a central component in clinical evaluation for medical devices. The clinical evaluation plan (CEP) is a foundational regulatory document that defines the scope, methodology, and objectives for the clinical evaluation. The evidence generated through this process underpins claims of safety and performance, informs post-market activities, and must withstand external scrutiny during regulatory review.
Despite its importance, literature review is often approached as a discrete task rather than a structured and ongoing process. This can lead to gaps in methodology, inconsistencies in documentation, and misalignment between relevant data and clinical claims – issues that may only become apparent during audit or submission assessment. The manufacturer is responsible for ensuring that the intended purpose and scope of the device are clearly defined and that all relevant data are included to support regulatory compliance.
These challenges are rarely the result of isolated errors. More often, they reflect the complexity of managing evidence across an evolving regulatory landscape, multiple data sources, and interconnected outputs such as Clinical Evaluation Reports (CERs) – the primary documents through which manufacturers demonstrate device safety and performance under EU MDR, post-market surveillance(PMS), and Post-Market Clinical Follow-Up (PMCF). A thorough understanding of clinical evaluation requirements and the regulatory landscape, including EU MDR standards, is essential for compliance and for producing accurate, audit-ready CERs. The initial step in creating a CER is defining the scope of the clinical evaluation and creating a Clinical Evaluation Plan (CEP), which outlines the devices, intended purpose, and target patient populations.
This article examines common literature review challenges in regulatory settings, focusing not only on what goes wrong but also on how these issues affect clinical evaluation and subsequent regulatory activities.
Why mistakes happen
The challenges associated with literature review in regulatory contexts are rarely the result of a single oversight. More often, they arise from the complexity of managing large volumes of evidence across multiple sources, combined with evolving regulatory expectations and the need to maintain alignment across interconnected outputs.
Fragmentation further contributes to this risk, particularly when literature search, data extraction, post-market surveillance, and reporting are managed across separate systems or teams. In such environments, maintaining consistency and traceability becomes increasingly difficult, and gaps in documentation or interpretation can emerge over time. Having a dedicated team and specialized team members, such as a CER writer or medical writer, is essential to ensure consistency, regulatory compliance, and high-quality clinical evaluation reports.
In addition, increasing pressure for rapid turnaround can lead to a focus on completion over quality. When timelines are constrained, there is a risk that methodological rigour is compromised, with insufficient attention given to search strategy development, documentation, or critical appraisal of evidence. The expertise and knowledge required for effective CER writing are crucial for maintaining quality and compliance, directly impacting business outcomes and regulatory success. Over time, this can weaken the reliability of the evidence base and increase the likelihood of issues arising during regulatory review.
Core mistakes
The following sections outline commonly encountered challenges in literature review processes, together with their potential impact on clinical evaluation and regulatory outcomes.
When Search Strategies Lack Clinical Alignment
Literature searches that are not clearly aligned with the device's intended use, target population, and clinical claims can result in the inclusion of irrelevant or low-value evidence. Without a defined clinical focus, search outputs may become broad and unfocused, making it difficult to establish a coherent clinical argument. Conducting a systematic literature review is essential to ensure that all relevant published literature and available literature are identified, and it is critical to determine whether the literature review strategy is appropriate for the device and regulatory requirements.
Impact: This can weaken the link between evidence and claims within the Clinical Evaluation Report (CER), increasing the likelihood of challenges during regulatory review and requiring rework to justify the selection and relevance of included studies.
When Search Methodology Cannot Be Reproduced
A lack of transparency in how literature searches are conducted– including incomplete documentation of databases, search terms, filters, and inclusion/exclusion criteria – limits the reproducibility of the review process.
Impact: Regulatory bodies expect literature reviews to be traceable and reproducible. Gaps in documentation can lead to questions during audit or submission assessment, potentially delaying approval or requiring additional justification.
When Evidence Is Collected but Not Critically Appraised
The identification of relevant literature is only one component of the review process. When studies are included without a structured assessment of quality, relevance, and risk of bias, the resulting evidence base may lack depth and clinical context. Comprehensive analysis of clinical data, using sound research methodology, is required to ensure scientific rigor. Scientific writers play a key role in evaluating and synthesizing clinical data from clinical investigations and published literature to support regulatory submissions.
Impact: This can result in conclusions that are not sufficiently supported, reducing confidence in the clinical evaluation and leading to increased scrutiny from Notified Bodies. In such cases, the literature review may become descriptive rather than analytical, with studies summarised individually rather than synthesised into a coherent clinical narrative.
When Outputs Become Misaligned Across the Evidence Lifecycle
In environments where literature review, post-market surveillance, and reporting are managed separately, inconsistencies can arise between different regulatory documents.
Impact: Misalignment across CER, PMS, and PMCF documentation can introduce gaps in the overall clinical narrative, raising concerns during regulatory review and increasing the burden of reconciliation and rework.
When Data Extraction Lacks Consistency and Structure
Inconsistent approaches to extracting and recording data from included studies can result in variability in how evidence is interpreted and presented. Where data extraction is not guided by predefined criteria or structured templates, different reviewers may capture different levels of detail or apply varying interpretations to similar findings.
A consistent approach involves the use of standardised data extraction frameworks, with clearly defined fields for study characteristics, outcomes, and methodological quality. This supports alignment across studies and ensures that evidence is recorded in a comparable and reproducible manner.
Impact: This can affect the comparability of studies and the clarity of conclusions, reducing confidence in the evidence base and complicating subsequent analysis and reporting.
When Time Constraints Compromise Methodological Quality
Under pressure to meet tight timelines, key steps in the literature review process – such as comprehensive searching, thorough documentation, and critical appraisal – may be reduced or overlooked.
Impact: While this may accelerate initial completion, it often leads to gaps that are identified later during review or audit, resulting in delays, rework, and increased regulatory risk.
When Literature Review Is Treated as a One-Time Activity
Approaching literature review as a static, one-off exercise rather than an ongoing process can lead to outdated evidence being carried forward into regulatory documentation.
Impact: Failure to maintain up-to-date evidence can create inconsistencies across CER, PMS, and PMCF activities, particularly when new data emerges that is not reflected across all outputs. This may be identified during audits or periodic updates, requiring retrospective corrections.
When Evidence Selection Introduces Bias (The "Echo Effect")
Literature review processes that disproportionately include studies supporting the intended clinical claims, while excluding or underrepresenting contrary findings, can introduce bias into the evidence base.
Impact: This can result in an incomplete or unbalanced clinical evaluation, increasing the likelihood of challenge during regulatory review. Notified Bodies expect a transparent and objective assessment of all relevant evidence, including limitations and conflicting data.
Summary of Common Literature Review Challenges
It is important to note that the literature review process for a CER consists of two phases: the literature search and the evaluation of the available literature, both of which must be meticulously planned to ensure all relevant published literature is identified.
Conducting a systematic literature review requires specific skills, including the ability to analyze scientific articles for relevance, summarize clinical and scientific data effectively, and document all articles returned in searches, even those that are excluded.
The Role of Literature Review in Clinical Evaluation Reports
A Clinical Evaluation Report (CER) is the primary document through which medical device manufacturers demonstrate that their device is safe and performs as intended. At its core, the CER depends on a systematic, well-documented literature review — making the quality of that review directly proportional to the strength of the overall submission. CERs must be written or reviewed by qualified clinical evaluators with documented expertise in research methodology, medical writing, and the relevant clinical field, as required by EU MDR and MEDDEV 2.7/1 rev 4. Expert medical writers should possess in-depth knowledge of regulatory requirements, including relevant laws, regulations, and guidelines, to ensure that the CER complies with all standards. Creating a CER involves a structured process that includes the analysis of clinical data generated from clinical investigations and published literature, ensuring scientific rigor and comprehensive analysis. The challenges outlined in this article — from misaligned search strategies to inconsistent data extraction — do not remain isolated within the literature review process. They surface in the CER itself, where gaps in evidence, weak clinical justification, or insufficient critical appraisal become visible to Notified Bodies during conformity assessment.
Why This Matters for CER Quality and Regulatory Outcomes
The consequences of literature review deficiencies often become most apparent during regulatory review and audit, where both the evidence and the processes used to generate it are subject to scrutiny. Regulatory compliance with medical device regulations such as EU MDR is essential, as notified bodies will assess around 22 factors when reviewing a Clinical Evaluation Report, including the suitability and limitations of the clinical data provided regarding the device's safety and performance. In these settings, gaps in reproducibility, inconsistencies across documentation, or insufficient critical appraisal may prompt detailed questions, requests for clarification, or the need for additional supporting analyses.
In practice, this can result in delays to review timelines, increased workload to address deficiencies, and, in some cases, challenges in demonstrating that clinical conclusions are adequately supported. Where inconsistencies extend across Clinical Evaluation Reports (CERs), post-market surveillance (PMS), and Post-Market Clinical Follow-Up (PMCF) activities, the effort required to reconcile discrepancies can be substantial.
Evidence selection is also closely evaluated. It is necessary to determine the relevance and adequacy of clinical data to support the device's safety and clinical performance in the target market. The inclusion of non-relevant, low-quality, or insufficiently justified sources may raise concerns regarding the credibility of the evidence base, particularly where the rationale for inclusion or exclusion is not clearly documented.
Taken together, these issues reinforce that literature review is not assessed in isolation, but as part of a broader evaluation of the reliability and control of regulatory evidence generation processes.
What Happens After a CER Literature Review Mistake Is Identified
Even within structured systems, errors and gaps in literature review can occur. The complexity of managing large volumes of evidence across evolving regulatory requirements means that no process is entirely immune to oversight. The presence of an issue does not necessarily indicate a failure; rather, what matters is how the issue is identified, addressed, and incorporated into ongoing processes.
Early identification plays a critical role in limiting downstream impact. Internal audits, routine updates, and continuous review mechanisms provide opportunities to detect gaps in search strategy, documentation, or interpretation before they affect regulatory submissions. In this context, literature review is best understood as an iterative process, rather than a one-time activity.
Once identified, corrective actions should be structured and proportionate to the issue. This may include revisiting and refining search strategies, re-running literature searches, updating inclusion and exclusion criteria, or ensuring alignment across Clinical Evaluation Reports (CERs), post-market surveillance (PMS), and Post-Market Clinical Follow-Up (PMCF) documentation.
From a regulatory perspective, the proactive identification and resolution of issues is often viewed positively. It reflects a transparent and controlled approach to evidence management, demonstrating that processes are not only in place, but actively maintained. This is particularly relevant in audit settings, where the ability to identify and address gaps internally may support confidence in the overall system.
The effective management of errors contributes to continuous improvement. As new evidence emerges and regulatory expectations evolve, maintaining a structured and responsive approach to literature review helps ensure consistency, traceability, and the ongoing integrity of clinical evaluation across the product lifecycle.
Conclusion: Building a Stronger Approach to CER Writing and Clinical Evidence
Effective literature review is not defined solely by the absence of errors, but by the ability to manage complexity, maintain consistency, and respond to gaps as they arise. The challenges outlined in this article reflect the realities of working within evolving regulatory environments, where evidence must be continuously evaluated, aligned, and maintained.
As such, the focus extends beyond avoiding mistakes to how processes are designed, controlled, and improved over time. Approaches that support alignment across the evidence lifecycle are better positioned to meet evolving regulatory expectations, ensuring that clinical evaluation remains coherent, transparent, and responsive to new information.
For manufacturers investing in CER writing and clinical evaluation, the quality of the underlying literature review is not a secondary concern — it is the foundation on which the entire submission rests. In this context, the strength of a literature review lies not only in its execution, but in how it is sustained and integrated across regulatory processes. Hiring expert CER writers is ultimately cost-effective, as their regulatory writing skills streamline submissions, reduce review times, and minimize additional requests for information.
If you are preparing a clinical evaluation report or reviewing your current literature review processes, Citemeds supports medical device manufacturers with structured, audit-ready CER writing and literature review services that meet EU MDR expectations. Our team brings the expertise, knowledge, and educational background in medicine and regulatory writing required for high-quality CER documentation. Get in touch to discuss your requirements.
Frequently Asked Questions
What is a Clinical Evaluation Report (CER) and why is literature review central to it?
A Clinical Evaluation Report (CER) is the primary document through which medical device manufacturers demonstrate that their device is safe and performs as intended under EU MDR 2017/745. At its core, the CER depends on a systematic, well-documented literature review — making the quality of that review directly proportional to the strength of the overall submission. Without a robust literature review, the clinical evidence base underpinning the CER may be incomplete, inconsistent, or insufficiently justified to withstand Notified Body scrutiny.
What are the most common CER writing mistakes?
The most common mistakes in CER writing relate to the quality of the underlying literature review rather than the document itself. These include search strategies that are not aligned to the device's intended use, evidence that is collected but not critically appraised, inconsistent data extraction, and literature review being treated as a one-time activity rather than an ongoing process. Each of these issues surfaces directly in the CER, where gaps in evidence or weak clinical justification become visible during conformity assessment.
What does good CER medical writing look like?
Effective CER medical writing goes beyond compiling and summarising available evidence. It involves critically appraising the quality and relevance of included studies, synthesising findings into a coherent clinical narrative, and ensuring that conclusions are clearly supported by the evidence. The process should be transparent, reproducible, and aligned across all interconnected regulatory outputs including post-market surveillance and PMCF documentation.
How often should a CER be updated?
Under EU MDR, a CER is not a one-time document — it must be updated regularly to reflect new clinical evidence, changes in the state of the art, and post-market data. For higher-risk devices, this typically means annual updates. Treating the CER as a static document is one of the most common compliance risks manufacturers face, as outdated evidence can create inconsistencies across regulatory documentation that are identified during audits or periodic reviews.
What is the difference between CER writing and a literature review?
A literature review is the systematic process of identifying, screening, and critically appraising published clinical evidence relevant to a device. CER writing is the broader process of synthesising that evidence — alongside clinical investigation data, post-market data, and benefit-risk analysis — into a structured regulatory document. The literature review is therefore a foundational component of the CER, and weaknesses in the review process directly compromise the quality of the final document.
What happens if a CER fails to meet Notified Body expectations?
If a CER is found to be insufficient during conformity assessment, manufacturers typically receive requests for additional information or clarification, which can significantly delay regulatory timelines. In more serious cases, gaps in clinical evidence or methodology may require substantial rework of both the literature review and the CER itself. Common reasons for failure include insufficient critical appraisal of evidence, misaligned search strategies, and inconsistencies between the CER and other regulatory documentation such as the risk management file and PMS reports.
How does clinical evidence support regulatory submissions under EU MDR?
Clinical evidence under EU MDR must demonstrate that a device meets the general safety and performance requirements set out in Annex I of the regulation. This evidence is generated through a combination of literature review, clinical investigation data, and post-market data – all of which must be systematically evaluated and documented within the CER. The strength of the clinical evidence directly determines the robustness of the regulatory submission and the likelihood of a successful conformity assessment outcome.
