IMDRF Publishes Final Guidance on the Selection of Adverse Event Terminology
On 25 February 2026, the International Medical Device Regulators Forum (IMDRF) published the final document IMDRF/AET WG/N86 FINAL:2026 – “Considerations for the Selection of IMDRF Adverse Event Terminology” .
The guidance was developed by the IMDRF Adverse Event Terminology Working Group (AET WG) and provides clarification on the correct and consistent use of IMDRF adverse event codes for medical devices, including in vitro diagnostic devices (IVDs).
Objective of the Guidance
According to the document, the purpose is to:
Provide general coding principles for reporting adverse events using IMDRF terminology
Provide examples addressing common coding challenges
The guidance builds on IMDRF/N43 (terminologies for categorized Adverse Event Reporting) and supports harmonised global reporting practices .
The document specifies that it is not intended to address every possible coding scenario and that medical judgement and expertise should be applied.
IMDRF Terminology Structure
The IMDRF adverse event terminology is organised into seven groupings within four sets of terminologies:
A Codes – Medical Device Problem
G Codes – Medical Device Component
E Codes – Clinical Signs and Symptoms
F Codes – Health Impact
B Codes – Type of Investigation
C Codes – Investigation Findings
D Codes – Investigation Conclusions
The document states that reports are expected to include at least one code from each of the seven terminology groups .
Where information is unavailable, specific codes such as “Insufficient Information” or “Not Yet Determined” are provided within the terminology structure.
Key Coding Principles for Manufacturers
Selection of the Most Detailed Term
IMDRF codes follow a hierarchical structure. The document states that users should:
Select the lowest-level term that accurately reflects the issue
Review full code definitions before coding
Ensure alignment with the hierarchy
Parent terms may be used where necessary, but more specific child terms should be selected when applicable.
Coding Throughout the Investigation Process
The guidance clarifies that:
Codes may need to be updated during follow-up reporting
Incorrect codes should be replaced
Device Problem codes should reflect what was observed at the time of the adverse event
Certain “not yet determined” or “results pending” codes may be used in initial or follow-up reports but should not be used in final reports.
Health Effect Coding
The document specifies that:
Health Effect codes should only be selected where harm can be confirmed as related to the device
A specific code exists for “Death Not Related to Reported Adverse Event” (F29)
Pre-existing conditions should not be coded as adverse event outcomes
Where no patient is involved, appropriate non-clinical impact codes should be used
E codes (Clinical Signs and Symptoms) are harmonised with a subset of MedDRA terms, except in specific cases .
Investigation Coding
The guidance distinguishes between:
B codes – Methods of investigation
C codes – Findings of the investigation
D codes – Root cause conclusions
The D codes are designed to be broad. Multiple root cause codes may be selected where applicable.
Practical Examples Included
Section 7 provides 20 detailed coding examples covering scenarios such as:
Implant fractures
Device alarm issues
Battery problems
False negative IVD results
AI software misclassification
Manufacturing deficiencies
Known inherent risks
The examples demonstrate application of codes across all seven terminology groups.
Read the full document below.
