The International Medical Device Regulators Forum (IMDRF) has developed a globally harmonized terminology system for reporting adverse events related to medical devices, including in vitro diagnostics (IVDs). This comprehensive guide, prepared by the IMDRF Adverse Event Terminology Working Group (AET WG), provides essential direction for industry partners and healthcare providers on the correct application and consistent use of this terminology.
With over 6,000 identified rare diseases and millions of medical devices in daily use worldwide, standardized adverse event reporting is critical for public health safety.
1. Introduction: The Need for Harmonized Medical Device Terminology
Since the Global Harmonization Task Force (GHTF) published SG2/N54 in 2006, most member countries implemented adverse event reporting systems aligning with its general principles. Building on this foundation, the IMDRF Adverse Event Terminology Working Group developed globally harmonized terminology and codes for:
- Product problems
- Cause investigation
- Health effects
- Device components
The widespread use of a single, appropriate adverse event terminology and coding system is expected to improve signal detection and validation by adverse event management systems, enabling a faster response by both industry and regulatory authorities for public health safety .
The Core Challenge: As both regulators and industry work towards implementation of IMDRF terminology, there is a critical need for guidance on the correct application and consistent use of the terminology. This document addresses that need by providing:
- General coding principles for reporting adverse events using IMDRF codes
- Practical examples addressing common coding challenges
- Guidance applicable to all stakeholders (manufacturers, healthcare providers, regulators)
2. Scope and Purpose
This document is intended to provide guidance on the correct application and consistent use of the adverse event terminology. It serves multiple stakeholders:
| Stakeholder | Application |
|---|---|
| Manufacturers | Standardized reporting to multiple regulators; internal trend analysis |
| Healthcare Providers | Accurate initial reporting of device-related incidents |
| Regulatory Authorities | Consistent data aggregation and signal detection |
| Importers/Distributors | Proper coding of adverse events in their jurisdictions |
Important Note: This document is not intended to address every potential code selection scenario. Medical judgement, related expertise, and common sense should also be applied. Regional specific regulatory reporting requirements will need to be considered in conjunction with this guidance .
3. Overview of IMDRF Coding Structure
3.1 The Four Sets of IMDRF Terminologies
The complete IMDRF terminology comprises seven groupings within four distinct sets of terminologies and their associated alphanumeric codes. Table 1 summarizes these groupings and their hierarchical structure .
Table 1: Overview of the Four Sets of IMDRF Terminologies
| No. | Name of Terminology | Description | Coding System |
|---|---|---|---|
| 1 | Medical Device Problem (A Codes) | Terms/codes for describing problems (malfunction, deterioration of function, failure) of medical devices in pre- or post-market contexts | A[00[00][00] |
| 2 | Medical Device Component (G Codes) | Terms/codes for describing the component of the medical device involved in the adverse event/incident | G[00[00][00] |
| 3 | Health Effects – Clinical Signs and Symptoms or Conditions (E Codes) | Terms/codes for describing the clinical signs and symptoms or conditions of the affected person resulting from the adverse event | E[00[00][00] |
| 4a | Cause Investigation – Type of Investigation (B Codes) | Terms/codes describing the type or scope of investigation activities performed | B[00] |
| 4b | Cause Investigation – Investigation Findings (C Codes) | Terms/codes describing the actual condition, defect, or malfunction identified as the cause | C[00[00][00] |
| 4c | Cause Investigation – Investigation Conclusion (D Codes) | Terms/codes describing the identified root cause of the event | D[00[00] |
| 3 (continued) | Health Effects – Health Impact (F Codes) | Terms/codes describing the consequences on the person affected | F[00] |
3.2 The Coding Sequence
Figure 1 in the original document illustrates the sequence in which IMDRF codes should be used, progressing from:
- Initial event description (A and G codes describing what happened to the device)
- Health effects documentation (E and F codes describing what happened to the patient)
- Investigation process (B codes describing how the investigation was conducted)
- Investigation findings (C codes describing what was found)
- Investigation conclusions (D codes describing the root cause)
4. General Term Selection Principles
4.1 Select the Most Detailed Level Term
IMDRF codes follow a hierarchical structure where higher-level terms describe general issues, and lower-level terms provide specific details. Select the lowest-level term that accurately describes the issue .
Example 1:
| Reported Narrative | IMDRF Terms [codes] Options | Best Choice |
|---|---|---|
| False positive patient sample | Incorrect, Inadequate or Imprecise Result or Readings [A0908] | |
| False Positive Result [A090804] | ✓ |
Example 2:
| Reported Narrative | IMDRF Terms [codes] Options | Best Choice |
|---|---|---|
| Little pieces of the device break off when adjusting the strap | Break [A0401] | |
| Material Fragmentation [A040103] | ✓ |
Important Principle: If a parent term is selected, then all child terms nested under that term should be considered similar types of events. This hierarchical structure allows for consistent grouping and analysis, enabling earlier identification of trends and safety signals .
4.2 Include at Least One Code from Each Group on All Reports
Where no exact match can be found or there is insufficient information, the following “placeholder” codes can be used :
| Terminology Group | Code for Insufficient Information |
|---|---|
| Medical Device Problem (A) | A26 – Insufficient Device Problem Information |
| Type of Investigation (B) | B21 – Type of Investigation Not Yet Determined |
| Investigation Findings (C) | C21 – Results Pending Completion of Investigation |
| Investigation Conclusions (D) | D16 – Conclusion Not Yet Available |
| Clinical Signs/Symptoms (E) | E2401 – Insufficient Information |
| Health Impact (F) | F24 – Insufficient Health Impact Information |
| Medical Device Component (G) | G07003 – Insufficient Component Information |
| Any Group | Appropriate Term/Code Not Available (A27/C22/D17/E2402/F28/G07002) |
Example of Complete Coding with Limited Information:
| Terminology Group | Code Selected |
|---|---|
| Medical Device Problem | A26 – Insufficient Device Problem Information |
| Type of Investigation | B21 – Type of Investigation Not Yet Determined |
| Investigation Findings | C21 – Results Pending Completion of Investigation |
| Investigation Conclusions | D16 – Conclusion Not Yet Available |
| Clinical Signs/Symptoms | E2401 – Insufficient Information |
| Health Impact | F24 – Insufficient Health Impact Information |
| Medical Device Component | G07003 – Insufficient Component Information |
4.3 Codes May Change During the Investigation
Changes in the patient’s condition, follow-up information, or investigation results may require updating the reported coding. When this happens, a new report updating or complementing the codes previously submitted should be provided .
Example: Inoperable Ventilator
| Report Type | Reported Narrative | IMDRF Terms [codes] |
|---|---|---|
| Initial | Inoperative condition on ventilator; “Unable to write to Event Log” observed | Data Problem [A1107] + Insufficient Device Problem Information [A26] |
| Follow-up | Ventilator didn’t start up properly; booted up endlessly | Data Problem [A1107] + Failure to Power Up [A070803] |
Note: The Problem Codes provided in a follow-up report should always reflect the problems that were observed at the time of the adverse event .
4.4 Quality Assurance
Consistent coding practices are key in facilitating effective terminology standardization. Organizations should have:
- Organization-wide term selection methods
- Quality assurance procedures in internal guidelines consistent with this document
- Training programs for staff assigning adverse event codes
4.5 Additional Codes and Terms
If you regularly find yourself selecting “code not available,” you may need to suggest a new term by submitting a change request through the IMDRF maintenance process .
Important Note: Manufacturers may develop more specific terms for internal post-market surveillance data. These additional terms should be child terms of existing IMDRF terms so that the IMDRF terms can be used for regulatory reporting.
5. Specific Term Selection Guidelines
5.1 Medical Device Problem (A Codes)
Question Answered: “What was the observed problem with the medical device?”
Key Principle: Terms should be factual and not speculative. Do not code normal device function as a malfunction .
Example: Distinguishing Normal Function from Malfunction
| Reported Narrative | Incorrect Coding | Correct Coding | Rationale |
|---|---|---|---|
| Device alarmed low battery and shut down, even though battery was freshly charged | Device Alarm System [A1601] | Premature Discharge of Battery [A070504] + Unexpected Shutdown [A0719] | The alarm is the intended protective measure; the problem is premature battery discharge |
5.2 Medical Device Component (G Codes)
Question Answered: “What part or component of the medical device was involved in, or suspected to have been involved in or affected by the adverse event?”
G terms can be used in combination with both device problem codes (A) and investigation codes (B, C, D) .
Example: Battery Depletion Investigation
| Report Type | Narrative | IMDRF Terms [codes] |
|---|---|---|
| Initial | Device explanted due to premature battery depletion | Battery [G02002] + Premature Discharge of Battery [A070504] |
| Final | Analysis identified anomalous capacitor as root cause | Capacitor [G0201201] + Electrical/Electronic Component Problem Identified [C0201] + Cause Traced to Component Failure [D02] |
5.3 Health Effects (E & F Codes)
Question Answered: “What happened to the patient (or other person affected) as a result of the incident or use of the device?”
5.3.1 Clinical Signs and Symptoms (E Codes)
Key Principles:
- Do not code pre-existing conditions or conditions the device is intended to treat
- Code provisional diagnoses; update if diagnosis changes
- Multiple codes can be used to capture a condition, provided each term is individually accurate
- If a single term captures both site and type of problem, use that single term
Example: Preexisting Conditions
| Reported Narrative | Correct Coding | Incorrect Coding |
|---|---|---|
| Paraplegic patient’s wheelchair malfunctioned; patient fell, admitted with suspected intracranial hemorrhage; later diagnosed with concussion | Initial: Fall [E2007] + Intracranial Hemorrhage [E0118] Follow-up: Fall [E2007] + Concussion [E0108] | Paraplegia [E012203] (preexisting condition should not be coded) |
Example: Combination Terms
| Reported Narrative | Option 1 | Option 2 (Best) |
|---|---|---|
| Patient developed fungal eye infection | Fungal Infection [E1902] + Eye Infections [E0818] | Corneal Perforation [E0811] |
5.3.2 Health Impact (F Codes)
Question Answered: “What were the consequences of the adverse event on the person affected?”
Key Principles:
- Do not select every applicable term; if there were both minor and serious injury, code only the more serious
- Multiple codes can be selected where they do not imply one another
- Be mindful of the difference between incidents with and without patient involvement
| Scenario | Appropriate Code |
|---|---|
| No patient consequences | No Health Consequences or Impact [F26] (plus E2403 – No Clinical Signs, Symptoms or Conditions) |
| Issue identified during maintenance | Problem Identified During Non-Clinical Procedure [F27] |
| Death occurred but unrelated to device | Death Not Related to Reported Adverse Event [F29] |
5.4 Manufacturer’s Cause Investigation (B, C & D Codes)
These three code sets together detail the cause investigation, broken down into method, results, and conclusion.
5.4.1 Type of Investigation (B Codes)
Question Answered: “What methods have been or will be used to investigate the incident?”
Example: Multiple Investigation Types
| Reported Narrative | B Codes Selected |
|---|---|
| Device returned for analysis; photos provided; testing performed; batch record review; user follow-up | Testing of Actual/Suspected Device [B01] + Analysis of Information Provided by User/Third Party [B15] + Analysis of Production Records [B14] + Historical Data Analysis [B11] |
5.4.2 Investigation Findings (C Codes)
Question Answered: “What are/were the results of the manufacturer’s investigation?”
Example: Water Damage Findings
| Reported Narrative | C Codes Selected |
|---|---|
| Device displayed critical error code; water damage and corrosion found on PCBA; cracks in waterproofing/case | Degradation Problem Identified [C0601] + Leakage/Seal [C0703] |
5.4.3 Investigation Conclusions (D Codes)
Question Answered: “What was concluded as the root cause of the reported event?”
D terms are designed to be broad. Regulators may require more detail in the report text, but the IMDRF code should reflect the general category.
| Root Cause Description | Appropriate D Code |
|---|---|
| Loose nozzle on widget extrusion system | Cause Traced to Manufacturing [D03] |
| Patient non-compliance with postoperative restrictions | Cause Traced to User [D04] |
| Known inherent risk materialized | Known Inherent Risk of Device [D12] |
| Random component failure with no specific cause identified | Cause Not Established [D15] |
6. Coding Examples from Case Descriptions
The IMDRF document provides 20 detailed coding examples. Below are selected examples illustrating key principles.
6.1 Example 1: Broken Hip Stem Implant
Narrative: A patient with a hip implant fell during intensive sport activity, complaining of pain. X-ray revealed broken hip stem. Device explanted and replaced. Manufacturer confirmed breakage but no production issues; noted IFU warning against heavy-duty activities.
| Terminology Group | Code Selected | Rationale |
|---|---|---|
| Clinical Signs/Symptoms | E2330 – Pain | Patient complained of pain |
| Medical Device Problem | A0401 – Break | Stem was broken |
| Health Impact | F1905 – Device Revision or Replacement | Device explanted and replaced |
| Type of Investigation | B01 – Testing of Actual/Suspected Device | Returned device evaluated |
| Type of Investigation | B14 – Analysis of Production Records | Lot record reviewed |
| Investigation Findings | C070603 – Separation Problem | Breakage confirmed |
Note: “Fall” is not coded as it was the cause of the incident, not the result.
6.2 Example 4: No Audible Alarm on Patient Monitor
Narrative: No audible alarm when SpO2 signal lost; only visual alarm displayed. No patient harm. Manufacturer review did not confirm allegation; device operated per specifications.
| Terminology Group | Code Selected |
|---|---|
| Medical Device Problem | A160102 – No Audible Alarm |
| Medical Device Component | G0600101 – Alarm, Audible |
| Clinical Signs/Symptoms | E2403 – No Clinical Signs, Symptoms or Conditions |
| Type of Investigation | B24 – Event History Log Review |
| Investigation Findings | C1902 – Device Problem Excluded |
| Investigation Conclusions | D15 – Cause Not Established |
6.3 Example 7: Fracture of Microcatheter During Surgery
Narrative: Microcatheter component broke during canaloplasty; 12mm fragment removed intra-operatively, extending surgery. Investigation revealed no manufacturing issue; catheter damaged by other surgical instrumentation.
| Terminology Group | Code Selected |
|---|---|
| Medical Device Problem | A0401 – Break + A0413 – Material Separation |
| Medical Device Component | G04023 – Catheter |
| Clinical Signs/Symptoms | E2401 – Insufficient Information |
| Health Impact | F23 – Unexpected Medical Intervention + F1908 – Prolonged Surgery |
| Type of Investigation | B01 – Testing of Actual/Suspected Device |
| Investigation Findings | C070603 – Separation Problem |
| Investigation Conclusions | D20 – Cause Traced to Another Device |
| Medical Device Component | G04112 – Rod/Shaft |
6.4 Example 8: False Negative Test Result in Proficiency Testing
Narrative: Multiple testing sites reported false negative results for same specimen in external quality assessment. No patient involved. Specimen contained uncommon genetic variant not accounted for in product development.
| Terminology Group | Code Selected |
|---|---|
| Medical Device Problem | A090803 – False Negative Result |
| Clinical Signs/Symptoms | E2403 – No Clinical Signs, Symptoms or Conditions |
| Health Impact | F27 – Problem Identified During Non-Clinical Procedure |
| Type of Investigation | B02 – Testing of Device from Same Lot/Batch + B15 – Analysis of Information Provided by User/Third Party |
| Investigation Findings | C1403 – Problem Related to Variant/Mutant |
| Medical Device Component | G01003 – Device Ingredient or Reagent |
6.5 Example 15: Balloon Catheter Failed to Deflate
Narrative: Balloon catheter failed to deflate during surgery; surgeon pierced balloon with guide wire to remove, extending surgery time. No patient injury. Manufacturer tested retained samples; balloon material out of specifications for stiffness.
| Terminology Group | Code Selected |
|---|---|
| Medical Device Problem | A140101 – Failure to Deflate |
| Medical Device Component | G04010 – Balloon |
| Health Impact | F1906 – Modified Surgical Procedure + F1908 – Prolonged Surgery |
| Clinical Signs/Symptoms | E2403 – No Clinical Signs, Symptoms or Conditions |
| Type of Investigation | B02 – Testing of Device from Same Lot/Batch |
| Investigation Findings | C0603 – Inadequate Physicochemical Properties |
| Investigation Conclusions | D03 – Manufacturing Deficiency |
6.6 Example 20: Artificial Intelligence Software Failure in Chest X-Ray
Narrative: AI software failed to flag pneumonia in elderly COPD patient, leading to delayed diagnosis and ICU admission. Investigation revealed algorithm bias from underrepresentation of elderly with comorbidities in training data.
| Terminology Group | Code Selected |
|---|---|
| Medical Device Problem | A090803 – False Negative Result |
| Medical Device Component | G02008 – Computer Software |
| Type of Investigation | B24 – Event History Log Review + B15 – Analysis of Information Provided by User/Third Party |
| Investigation Findings | C1010 – Artificial Intelligence Training/Validation Problem Identified |
| Investigation Conclusions | D19 – Cause Traced to Artificial Intelligence Training/Validation Process |
| Clinical Signs/Symptoms | E0733 – Pneumonia |
| Health Impact | F13 – Misdiagnosis/Misclassification + F04 – Delay to Diagnosis + F05 – Delay to Treatment/Therapy + F30 – Disease Progression + F07 – Exacerbation of Existing Condition |
7. Practical Implications and Best Practices
7.1 For Manufacturers
| Practice | Benefit |
|---|---|
| Implement consistent coding procedures globally | Streamlined reporting to multiple regulators |
| Develop internal child terms for more specific tracking | Better internal trend analysis while maintaining IMDRF compatibility |
| Train all staff involved in adverse event reporting | Reduced coding errors and more reliable data |
| Participate in IMDRF maintenance processes | Influence future terminology development |
7.2 For Healthcare Providers
| Practice | Benefit |
|---|---|
| Provide detailed narratives in initial reports | Enables accurate coding from the start |
| Include device identification information | Facilitates manufacturer investigation |
| Report all suspected device-related incidents | Contributes to global signal detection |
7.3 For Regulators
| Practice | Benefit |
|---|---|
| Encourage consistent use of IMDRF terminology | Improved cross-border data comparability |
| Provide feedback on coding challenges | Continuous improvement of guidance |
| Monitor trends using IMDRF-coded data | Earlier identification of safety signals |
8. Useful Resources and Links
| Resource | Description | URL |
|---|---|---|
| IMDRF Documents | All IMDRF publications | http://www.imdrf.org/documents/documents.asp |
| IMDRF Maintenance | Process for submitting change requests | https://www.imdrf.org/working-groups/adverse-event-terminology/imdrf-adverse-event-terminology-maintenance |
| IMDRF Code Browser | Searchable database of IMDRF codes | https://www.imdrf.org/working-groups/adverse-event-terminology/imdrf-adverse-event-terminology-web-browser |
| MedDRA Documentation | Support for MedDRA users | https://www.meddra.org/how-to-use/support-documentation |
| Training Quiz | Test understanding of this document | IMDRF Website Training section |
9. Conclusion: The Future of Medical Device Safety Monitoring
The IMDRF Adverse Event Terminology represents a significant advancement in global medical device safety monitoring. By providing a standardized language for describing device problems, patient outcomes, and investigation findings, this terminology enables:
- More efficient signal detection across multiple regulatory jurisdictions
- Faster response to emerging safety concerns
- Better trend analysis at global, regional, and local levels
- Improved communication between manufacturers, healthcare providers, and regulators
- Enhanced patient safety through more robust post-market surveillance
As the document emphasizes, “medical judgement, related expertise, and common sense should also be applied” alongside the coding guidance. The terminology is a tool—powerful but dependent on the skill and knowledge of those who use it.
For manufacturers, healthcare providers, and regulators, mastering this terminology is not just a compliance exercise; it is a commitment to patient safety and public health. As medical devices become increasingly sophisticated—incorporating artificial intelligence, advanced materials, and novel technologies—the importance of accurate, consistent adverse event reporting will only grow.
The IMDRF Adverse Event Terminology Working Group continues to maintain and evolve these terminologies, responding to user feedback and emerging needs. All stakeholders are encouraged to participate in this process, ensuring that the language of medical device safety keeps pace with the devices it describes.
