Why Deficiency Letters Keep Coming After Your Response

Written by HATEM RABEH, MD, MSc Ing

Your Clinical Evaluation Expert And Partner

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I see this pattern regularly. A manufacturer receives a deficiency letter from the Notified Body. The team mobilizes. They write detailed responses. They add documents. They submit within the deadline. Then they wait. When the next letter arrives, the frustration is real. The responses were complete. The documents were attached. Yet the issues persist.

The problem is not effort. The problem is understanding what the reviewer is actually looking for.

What a Deficiency Letter Actually Means

A deficiency letter is not a checklist. It is a signal that the reviewer could not reach a conclusion based on what was submitted. The letter describes the gap between what they found and what they need to justify their assessment.

Most deficiency letters cite specific MDR requirements. Article 61 for clinical evaluation. Annex XIV for documentation structure. MDCG 2020-13 for clinical investigation requirements. These citations are not decorative. They tell you which regulatory obligation the reviewer believes is not met.

But here is what many teams miss. The citation tells you the rule. The deficiency describes the consequence. The actual concern is often unstated. It sits between the lines. If you only respond to what is written, you miss what is needed.

Why Surface-Level Responses Fail

The most common mistake is responding at the same level as the deficiency. The letter says the clinical data is insufficient. The team adds more studies to the list. The letter says the risk analysis is incomplete. The team adds more rows to the table. The letter says the PMCF plan lacks detail. The team expands the text.

None of this works if the underlying reasoning is flawed.

Consider a deficiency that states: “The equivalence demonstration does not adequately address differences in materials.” A weak response adds a paragraph comparing material properties. A strong response reassesses whether equivalence can be claimed at all, and if so, reconstructs the entire equivalence argument with clinical and technical justification that closes the gap.

The weak response answers the sentence. The strong response addresses the concern. The concern is that the reviewer cannot accept your device as equivalent because the technical differences create clinical uncertainty. Until that uncertainty is resolved, no amount of additional text will close the deficiency.

The Structure of a Response That Works

A response that actually resolves deficiencies follows a clear structure. It starts by acknowledging what the reviewer could not conclude. It then presents the reasoning that allows that conclusion to be reached. Finally, it points to the specific location in the documentation where this reasoning is now captured.

Let me show you what this looks like in practice.

Suppose the deficiency states: “The State of the Art review does not sufficiently demonstrate that all relevant alternatives have been considered.”

A typical response might say: “Additional alternatives have been added to Section 6.2 of the CER. The SOTA now includes 12 device categories instead of 8.”

This response describes what was done. It does not explain why the concern is resolved. The reviewer does not know if these 12 categories are sufficient. They do not know if the search strategy was systematic. They do not know if the clinical context was adequately considered.

A strong response would say: “The SOTA review has been reconstructed using a systematic literature search combined with review of device databases and clinical guidelines. The search strategy is described in CER Section 4.1. The resulting device categories were validated against the intended clinical use and patient population defined in the IFU. Each category is evaluated for clinical safety and performance in CER Section 6.2. This ensures all clinically relevant alternatives have been identified and assessed per MDCG 2020-13 Section 5.1.”

This response explains the logic. It shows the reviewer how the concern was addressed at the root. It references both the documentation and the regulatory expectation. Now the reviewer can verify that the approach is sound.

Reading Between the Lines

Some deficiency letters are direct. Others require interpretation. When a reviewer writes that evidence is “insufficient,” they are not always asking for more evidence. Sometimes they are signaling that the evidence does not match the claim.

For example, a deficiency might state: “The clinical data provided does not adequately support the intended purpose.”

This can mean several things. It might mean the clinical data comes from studies with different patient populations. It might mean the endpoints measured do not align with the performance claims. It might mean the follow-up duration is too short to assess long-term safety. It might mean the data is old and no longer representative of current clinical practice.

If you respond by adding more studies without addressing which of these concerns applies, you are guessing. If you guess wrong, the deficiency returns.

The solution is to analyze the intended purpose statement, the clinical data summary, and the claim structure in your CER. Ask yourself: if I were reviewing this for the first time, could I conclude with confidence that this device is safe and performs as intended for this specific patient population?

If the answer is not clearly yes, then you know where the gap is.

Handling Requests for Justification

Many deficiencies ask for justification. “Justify why no clinical investigation is required.” “Justify the choice of equivalence pathway.” “Justify the PMCF sample size.”

These are not invitations to write more. They are signals that the rationale you provided was not convincing. The reviewer read your justification and did not find it sufficient to support your decision.

A weak justification presents a conclusion. A strong justification presents the reasoning that leads to the conclusion. The difference is evidence and logic.

For example, if you claim no clinical investigation is needed because sufficient clinical data exists, the reviewer needs to see why that data is sufficient. This means showing that the data covers the relevant patient population, the intended use, the duration of use, and the critical safety and performance aspects. It means demonstrating that the data is current and applicable to your device.

Simply stating “sufficient data exists” does not allow the reviewer to verify your reasoning. Pointing to the data, explaining its relevance, and mapping it to your clinical claims does.

The Role of the Clinical Evaluation Report

Most deficiency letters point back to the CER. The CER is the single document that must demonstrate the device meets the safety and performance requirements under MDR Article 61. If the CER has gaps, deficiencies will appear.

The problem is that many CERs are written as reports of what was done rather than demonstrations of what was concluded. The reviewer does not need a report. They need a structured argument that allows them to reach the same conclusion you reached.

This means the CER must do three things clearly. First, it must define what needs to be demonstrated. This comes from the intended purpose and the claims. Second, it must present the evidence and analysis that supports each claim. Third, it must conclude whether the benefit-risk profile is favorable and whether the device meets its intended purpose.

If any of these three elements is weak, the deficiency will target it.

When you receive a deficiency that points to the CER, do not add sections. Reassess whether the CER structure allows the reviewer to follow your reasoning from claim to evidence to conclusion. If it does not, restructure it.

Writing the Response Document

The response document itself matters. I have seen responses that are difficult to follow. Multiple attachments. References to previous submissions. Long explanations without clear structure. The reviewer must work to understand what changed and why.

A strong response document is structured to make the reviewer’s job easier. It lists each deficiency. It provides a direct response that explains how the issue is resolved. It references the updated section of the technical documentation. It includes a brief summary of what changed and why the change addresses the root concern.

This is not about formatting. It is about clarity. The reviewer should be able to read your response, verify the change in the documentation, and conclude that the deficiency is closed. If they have to search for information or interpret your intent, the response is not clear enough.

One technique that works well is to structure each response in three parts. First, acknowledge the concern. Second, explain what was changed and why. Third, direct the reviewer to the exact location where the change can be verified. This structure ensures nothing is left ambiguous.

When the Issue Is Structural

Some deficiencies cannot be resolved with additional text or minor updates. They signal that the approach itself is flawed. The equivalence pathway was not appropriate. The clinical data is fundamentally insufficient. The risk analysis does not align with the clinical evaluation.

When this happens, there is no shortcut. The technical documentation must be revised at a structural level. This is not what manufacturers want to hear when they are under timeline pressure. But it is reality.

Attempting to patch a structural issue with incremental changes leads to more deficiency letters. Eventually the Notified Body will conclude that the submission cannot proceed. At that point, the project is delayed far longer than it would have been if the structural issue had been addressed immediately.

I have worked with manufacturers who spent six months responding to deficiencies before finally accepting that the equivalence claim was not valid. Once they shifted to generating new clinical data, the path became clear. The lesson is that recognizing a structural issue early saves time.

Communicating With the Notified Body

Most deficiency letters include a deadline for response. Some manufacturers treat this as a one-way process. They submit the response and wait. But communication with the Notified Body does not have to be passive.

If a deficiency is unclear, ask for clarification before responding. If you believe the concern requires a change in clinical strategy, outline your proposed approach and confirm it with the Notified Body before committing resources. If the response will take longer than the deadline allows, communicate early and explain why.

Notified Bodies are not adversaries. They are reviewers working under regulatory constraints. Clear communication reduces misunderstandings and prevents wasted effort.

That said, every interaction should be professional and documented. Verbal discussions should be followed by written summaries. Agreements should be confirmed in writing. This protects both parties and creates a clear record.

What Happens After You Submit

Once the response is submitted, the Notified Body reviews the updated documentation. If the deficiencies are resolved, the assessment continues. If they are not, another letter is issued.

The key is understanding that each round of deficiencies is not a failure. It is part of the conformity assessment process. The goal is not to avoid deficiencies. The goal is to resolve them systematically so the assessment can proceed.

That means approaching each deficiency letter as a diagnostic tool. It tells you where the documentation does not yet meet regulatory expectations. Your response should close that gap completely, not provisionally.

If you find yourself responding to the same issue multiple times, stop and reassess. Either the response is not addressing the root concern, or the documentation itself has a flaw that cannot be patched incrementally. In either case, more text will not solve the problem.

Final Thought

Responding to deficiency letters is not about writing faster or adding more pages. It is about understanding what the reviewer needs to reach a conclusion and providing it clearly and completely.

This requires reading the deficiency carefully, identifying the root concern, and addressing it at the level of reasoning and evidence. It requires aligning your response with both the regulatory expectation and the reality of your device. And it requires being honest about when the issue is structural rather than editorial.

When you approach deficiencies this way, the letters stop repeating. The assessment moves forward. And the technical documentation becomes stronger in the process.

The next time you receive a deficiency letter, ask yourself: am I responding to what was written, or am I resolving the concern behind it? That distinction determines whether the issue closes or returns.

Peace,
Hatem
Clinical Evaluation Expert for Medical Devices
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