What Should a Medical Device Complaint Investigation Include?
A Completed Investigation Is Not Always an Adequate Investigation.
A complaint file can contain an investigation section, a conclusion and an approval signature and still fail to explain what actually happened.
Investigation adequacy is not simply about completing workflow fields. It depends on whether the evidence, reasoning and traceability support the conclusion. The investigation should also be proportionate to the device, event, patient or user impact, and potential consequence of recurrence.
Lack of a proper investigation will lead to closure without adequate evidence, lack of reportability, recurrence, delayed CAPA, poor escalation of supplier or inspection findings.
A root cause doesn’t have to be conclusively established in all cases, but any level of uncertainty must be documented and managed.
For companies that require an independent review of their complaints, our Medical Device Complaint Handling and Vigilance Review Services could assist in conducting investigations, reportability, downstream actions, and closure reviews.
What should a medical-device complaint investigation include?
Clear description of the complaint
Start with the actual event:
⦿ What was reported?
⦿ Who reported it?
⦿ When and where did it occur?
⦿ How was the device being used?
⦿ What was it expected to do?
⦿ What allegedly failed?
⦿ What happened to the patient or user?
⦿ What immediate action was taken?
The investigation should distinguish the customer’s statement, confirmed facts, assumptions, and missing information. This prevents an allegation from becoming an unsupported fact in the investigation record.
Complete device identification
Record available information such as:
⦿ Device name and model
⦿ Lot, batch or serial number
⦿ Software version
⦿ Manufacturing date
⦿ Supplier or component information
⦿ Service history
⦿ Market and applicable labeling version
This information allows the manufacturer to identify affected units, review manufacturing history, assess supplier involvement and compare similar complaints.
Patient, user and use-context information
Consider the patient or user outcome, user type, clinical setting, intended use and whether the device was relied upon for diagnosis or treatment.
Also consider whether another device or intervention prevented harm, whether instructions were followed and whether foreseeable use error may have contributed.
The same technical failure can have very different implications depending on how and where the device was being used.
Device and technical evaluation
Where the device is available, the investigation may include:
⦿ Visual inspection
⦿ Functional testing
⦿ Testing against specifications
⦿ Software or log review
⦿ Component analysis
⦿ Battery or power-system assessment
⦿ Alarm or sensor testing
⦿ Calibration or service review
Testing should address the reported failure. A generic statement that the device “passed testing” does not necessarily explain why the reported problem occurred.
Manufacturing, Batch and Supplier Review
Identify all relevant manufacturing and supplier information, such as:
⦿ Device history or batch records
⦿ Release information
⦿ Deviations and nonconformances
⦿ Rework
⦿ Process or equipment changes
⦿ Supplier changes
⦿ Incoming inspection results
⦿ Supplier nonconformances
⦿ Similar failures associated with the same lot or component
Similar-event and trend review
Consider previous complaints involving the same failure mode, product, variant, lot, supplier, market or user group.
Complaint frequency, complaint rate, recurrence and increasing severity may also provide important context.
For the broader trend-assessment approach, see When Do Repeated Medical Device Complaints Become a Trend?
Risk and reportability assessment
This investigation should allow evaluation of:
⦿ Reportability
⦿ Potential consequences of recurrence
⦿ Risk-control effectiveness
⦿ CAPA
⦿ Supplier or engineering escalation
⦿ Post-market surveillance implications
Investigation and reportability review may proceed in parallel. A reportability decision should not necessarily wait until every technical question has been resolved.
For the reportability framework, see Which Medical Device Complaints Are Reportable, and Which Authority Should Be Notified?.
FDA also links complaint evaluation with Medical Device Reporting: manufacturers must maintain complaint files and evaluate complaints to determine whether an event is reportable. FDA’s current QMSR became effective February 2, 2026, incorporating ISO 13485:2016 into the FDA quality-system framework.
How do you know whether a medical device complaint investigation is adequate?
Does It Address the Actual Complaint?
Ask whether the reported failure was actually evaluated, whether the investigation focused on the event described by the reporter and whether the conclusion explains the customer’s experience.
Testing unrelated characteristics of a device should not be used as evidence that the reported failure was adequately investigated.
Is the Investigation Proportionate to Risk?
Investigation depth should reflect:
⦿ Severity
⦿ Potential consequence of recurrence
⦿ Device criticality
⦿ Patient dependence
⦿ Complaint history
⦿ Supplier or manufacturing involvement
⦿ Regulatory significance
A low-risk cosmetic issue does not necessarily require the same depth as a failure affecting diagnosis, treatment or a safety function.
Is the evidence traceable?
The file should identify:
⦿ Records reviewed
⦿ Tests performed
⦿ Methods used
⦿ Results obtained
⦿ Supporting records
⦿ Individuals or functions involved, where appropriate
Another reviewer should be able to trace the way from the evidence to the conclusion.
Were reasonable alternative causes considered?
Reasonable alternative causes could be:
⦿ Design
⦿ Manufacturing
⦿ Supplier components
⦿ Software
⦿ Packaging
⦿ Labeling
⦿ Use error
⦿ Maintenance or servicing
⦿ Storage or transportation
⦿ Environmental conditions
The first convenient explanation should not automatically become the root cause.
Were similar complaints evaluated?
An apparently isolated event may become more significant when reviewed alongside previous complaints, service records, nonconformances, CAPA, supplier issues, production deviations or PMS information.
For more on recurring complaint evaluation, see medical device complaint trends
Does the conclusion match the evidence?
The conclusion should make its level of certainty clear. Depending on the evidence, the cause may be confirmed, probable, possible, inconclusive or unknown.
“No fault found” should describe an evidence-based outcome – not an absence of meaningful investigation.
Are Downstream Actions Addressed?
The investigation should identify whether the complaint requires:
⦿ CAPA
⦿ Risk-management review
⦿ Supplier action
⦿ Engineering review
⦿ Servicing or maintenance changes
⦿ Labeling or training updates
⦿ Trend monitoring
⦿ Regulatory action
An adequate complaint investigation should explain what happened, what evidence was reviewed, which causes were considered, what conclusion is supported and what action is required next.
Is the Root-Cause Conclusion Supported?
Immediate Cause Versus Root Cause
An immediate cause is the direct technical or operational reason the event occurred.
A root cause is an underlying design, process, supplier, system or control issue that allowed the event to occur.
For example:
⦿ Immediate cause: insufficient battery output
⦿ Possible root cause: supplier component variation
⦿ Alternative cause: inadequate battery specification
⦿ Alternative cause: manufacturing or assembly issue
The investigation should not automatically treat the immediate cause as the root cause.
Match Certainty to Evidence
A conclusion should reflect the strength of the evidence.
For example, rather than stating:
“Battery failure caused the complaint.”
A stronger conclusion might explain the test evidence, relevant supplier-lot information and remaining uncertainty.
The investigation should ask:
⦿ Was the failure reproduced?
⦿ Is objective evidence available?
⦿ Were competing causes considered?
⦿ Does the conclusion explain the event sequence?
⦿ Do similar complaints support it?
⦿ Does the proposed action address the identified cause?
Is “User Error” Enough?
Not necessarily.
The investigation should consider whether instructions were clear, the use error was foreseeable, the design encouraged the error, training was adequate and labeling or usability controls were effective.
Is “no fault found” an adequate conclusion?
It may be appropriate only when the file documents the testing performed, test conditions, whether the reported condition could be reproduced, whether the correct device and configuration were evaluated, whether intermittent failure was considered and what uncertainty remains.
A recent FDA warning letter illustrates why documented evidence matters: FDA identified a complaint investigation where the manufacturer stated that measurements had been performed but could not produce retained measurement data supporting its conclusion.
Can a complaint be closed without a returned device?
Yes, potentially.
The absence of a returned device does not automatically prevent closure, but it should not automatically end the investigation either.
A device may not be returned because it was discarded, remains clinically necessary, was repaired, cannot be identified, is located in another country or cannot be shipped for logistical or safety reasons.
In the case that the device is not available, the following alternative evidence may include:
⦿ Photographs or videos
⦿ Device logs
⦿ Software data
⦿ Service records
⦿ User statements
⦿ Clinical records
⦿ Distributor information
⦿ Manufacturing and batch records
⦿ Supplier records
⦿ Similar complaints
⦿ Known failure modes
⦿ Remote diagnostic information
The document should explain why the device was not available and how alternative evidence was gathered, what limitations were created by the unavailability of the device.
Closure may not be appropriate simply because the device was not returned when serious harm occurred, the failure is recurring, reportability remains unresolved, a batch or supplier issue is possible or further investigation is reasonably possible.
The key question is not “Was the device returned?”
It is “Do we have enough reliable evidence to reach and document a defensible conclusion?”
What evidence is required before complaint closure?
Confirm whether the complaint was assessed within the applicable quality-system processes, including FDA 21 CFR Part 820 – Quality System Regulation, for:
Complaint completeness
Confirm:
⦿ Complaint description
⦿ Device identification
⦿ Event and awareness dates
⦿ Reporter information
⦿ Patient or user outcome
⦿ Use context
⦿ Information requests and responses
⦿ Returned-device status
Investigation evidence
The document must have investigative method, evidence reviewed, tests performed with results, review of manufacture/batch if applicable, review of suppliers where applicable, evaluation of any other similar events, root cause assessment, limitations and attachments.
Regulatory evidence
Confirm the reportability assessment, market decision taken, reportability status where applicable, reason for non-reportability and reviewer approval.
Additional information about determining whether a complaint is reportable is available at medical device complaint reportability assessment.
Quality-system evidence
Assess whether CAPA, risk management, supplier quality, nonconformance, product change, labeling, training, maintenance, PMS or trend review are relevant.
This is where understanding why CAPA is important becomes critical.
CAPA must not be used simply to fix paperwork as part of the investigation of complaints and quality systems.
Closure Rationale
The closure rationale should answer:
⦿ What happened?
⦿ What was determined?
⦿ What remains uncertain?
⦿ Why is no further investigation required?
⦿ What actions were initiated?
⦿ Who owns remaining actions?
⦿ Why can the complaint close?
⦿ Who reviewed and approved closure?
A complaint may potentially close while related CAPA, supplier or product actions remain open when the complaint investigation is complete, reportability is resolved, related actions are formally linked, owners and due dates are assigned, and the actions remain controlled within the QMS.
The complaint should not be closed merely to improve overdue metrics while essential decisions remain unresolved.
Practical example: Recurring battery failures
It has been reported by some customers that a blood pressure monitor runs out of power suddenly. There are some instances where the device is not returned and uses batteries from the same manufacturer.
Weak conclusion
“Device not returned. Complaint closed as unconfirmed.”
Stronger investigation approach
⦿ Document retrieval attempts
⦿ Review photographs and user statements
⦿ Examine manufacturing and supplier-lot records
⦿ Review similar complaints
⦿ Test retained samples where available
⦿ Assess battery specifications and power consumption
⦿ Document remaining uncertainty
⦿ Determine whether supplier action, CAPA, risk review or maintenance changes are needed
The absence of the returned unit limits certainty but does not remove the obligation to investigate using available evidence.
Does your complaint process clearly identify when CAPA is needed?
Complaint investigations often identify issues that extend beyond a single event. Understanding why CAPA is important helps manufacturers address recurring failures, systemic issues and quality-system weaknesses.
Elexes supports manufacturers with CAPA evaluation, root-cause review and quality-system improvement.
Common complaint-investigation weaknesses
⦿ Restating the complaint instead of investigating it
⦿ Testing the device without addressing the reported failure mode
⦿ Using “no fault found” without documenting test conditions
⦿ Concluding “user error” without reviewing usability, labeling or training
⦿ Ignoring similar complaints
⦿ Failing to review manufacturing or supplier records
⦿ Selecting a root cause stronger than the evidence supports
⦿ Closing because the device was not returned
⦿ Failing to assess CAPA, risk or supplier escalation
⦿ Closing while reportability remains unresolved
What Should Be Documented in a Medical Device Complaint Investigation?
A defensible complaint file should allow another reviewer to understand:
⦿ What was reported
⦿ What was investigated
⦿ What evidence was obtained
⦿ What limitations remained
⦿ Why the conclusion was reached
⦿ Whether reportability was assessed
⦿ What downstream actions were considered
⦿ Why closure was justified
⦿ Who reviewed and approved the conclusion
There must be a link between complaint → investigation → evidence → conclusion → reportability → downstream action → closure.
An Adequate Investigation Is Evidence-Based
A completed workflow is not necessarily an adequate investigation.
A strong medical device complaint investigation addresses the actual complaint, uses relevant evidence, considers reasonable causes and makes the strength of the conclusion match the evidence.
While a returned product could help in the investigation process, a lack of it should not excuse the need for evidence-based review. Similarly, “No fault found” and “User error” should not be used to gloss over unresolved issues.
Before closure, the manufacturer should be able to explain not only what happened, but also why the conclusion is defensible, whether reportability has been resolved and whether the complaint requires CAPA, risk, supplier, product, PMS or other downstream action.
If a manufacturer wishes to have an independent review of their complaint evidence, investigations, and root cause analysis, explore Medical Device Complaint Handling and Vigilance Review Services.
Need Help Reviewing Your Complaint Investigations?
FAQs
Does every medical device complaint require a full investigation?
Not necessarily. Investigation depth should be proportionate to the complaint, device, risk, outcome, recurrence potential and applicable requirements. However, the manufacturer should have a documented basis for the investigation approach and closure decision.
What should a complaint investigation include?
It should cover the complaint information, identification of the device, usage context, patient or user consequence, technical data, manufacturing/supplier issues when appropriate, similar complaints, root cause, reportability and quality actions.
Can a complaint be closed without a returned device?
Yes, potentially. The manufacturer must show documentation of the efforts made to retrieve the device, substitute information available, constraints and why the available information allows resolving the complaint.
Is “no fault found” an acceptable conclusion?
Yes, as long as it is justified through testing and evaluation performed on the device. "No fault found" does not only imply that the device underwent testing.
Is “user error” an adequate root cause?
Not automatically. The investigation should consider foreseeable use, labeling, instructions, training, usability and whether the device design contributed to the event.
Can a complaint close while CAPA remains open?
Yes, if the complaint investigation is completed and reportability determined, if the link between the complaint and the CAPA is established, the responsible party for performing the CAPA and due date are assigned, and the CAPA is controlled within the QMS.
