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  6. MDR Adverse Event Codes
  1. Mandatory Reporting Requirements: Manufacturers, Importers and Device User Facilities

MDR Adverse Event Codes

The FDA MDR adverse event codes are collectively a system of codes, terms, and definitions used to describe and categorize medical device adverse events. They are primarily used to complete medical device reports (MDRs). They are divided into six separate types, each of which is organized hierarchically. In addition, the FDA MDR adverse event codes are related to two other coding systems: the National Cancer Institute Thesaurus (NCIt) and the International Medical Device Regulators Forum (IMDRF) Adverse Event Reporting terminologies.

Code Types

The FDA MDR adverse event codes are divided into the following six categories:

Name Purpose
Device Problem Code Describe device failures or issues related to the device during the reported event through observational language
Manufacturer Evaluation Method Code Describe the method of investigation of the device involved in the reported event
Manufacturer Evaluation Result Code Describe specific findings from the investigation of the device involved in the reported event, typically an explanation for the device problem observed
Manufacturer Evaluation Conclusion Code Describe conclusions from the investigation of the device involved in the reported event, typically a root cause for the device problem observed
Patient Problem Code Describe actual adverse effects on a patient that may be related to the device problem observed during the reported event
Device Component Code Describe specific device components or assemblies associated with the device problem observed during the reported event

Device Problem Code and Patient Problem Code are often referred to collectively as Event Problem Codes, due to the label on section F10 of the FDA Form 3500A. Manufacturer Evaluation Method Code, Result Code, and Conclusion Code are often referred to collectively as Evaluation Codes, due to the label on section H6 of the FDA Form 3500A.

Code Structure

Each set of codes is organized in a tree-like hierarchical structure, where higher-level (closer to the root) codes are more generic, while lower-level (leaf) codes are more specific. A parent code is often divided into multiple distinct and more-specific child codes, each of which can be considered a member of the set of problems or observations described by the parent code. This allows each set of codes to be intuitively organized in a way that accurately represents the relationship between different but similar codes.

Reporters should code to the lowest level possible; in other words, they should choose the most specific term(s) available in each category to describe the event or investigation. Reporters may choose more than one code from each set when filing their report, but there is no need to choose both a parent code and one of its children; by definition, the child code is a member or type of the problem or observation represented by its parent, so the child code alone is sufficient.

Each FDA code is represented by a numeric identifier from 2 to 4 digits in length. The numbers used for each code are assigned sequentially based on a set of internal guidelines, so the number assigned to each code does not have any bearing on the code's location within the hierarchy to which it belongs. In other words, codes with similar numbers are not necessarily related to each other.

NCI Thesaurus (NCIt)

Every FDA adverse event code is assigned a single, distinct NCIt Concept Code (sometimes referred to as a C-Code). These codes are listed on the National Cancer Institute Enterprise Vocabulary Services website and in the main NCI Thesaurus.

NCIt codes are used in various software applications to represent a wide range of medical terminology, including occupations, medical procedure locations, and report types. The Electronic Medical Device Reporting (eMDR) system uses these codes to represent the MedWatch FDA Form 3500A paper form as an XML document. For this reason, electronic MDR reporters may use FDA codes or NCIt codes when entering adverse event codes into the FDA Form 3500A XML document.


The FDA is currently participating in the IMDRF Adverse Event Reporting (AER) terminologies working group, which aims to improve and harmonize medical device adverse event coding among participating regulatory agencies. This working group is iteratively producing new code sets, which are posted to the IMDRF documents repository as new annexes on a singular guideline document. As each new annex is published, FDA intends to update the corresponding FDA code set to harmonize with the new IMDRF code set; as a result, each IMDRF code will map to a single, distinct FDA code.

At this time, the FDA's eMDR system is not configured to accept the IMDRF codes, however, once the IMDRF working group has published the initial version of all IMDRF code sets, the FDA plans to update eMDR to accept IMDRF codes, in addition to the FDA codes and NCIt codes that are currently accepted. This will be possible because all three (FDA, NCIt, and IMDRF) coding systems will be harmonized with a one-to-one mapping for each code across all three systems.

As part of the harmonization effort, FDA is no longer adding new adverse event codes in response to manufacturer requests. Manufacturers and other stakeholders who would like to request that a new adverse event code be added should follow the IMDRF code request process.

The FDA plans to achieve complete harmonization with IMDRF on September 7, 2020. On that date, the FDA will be harmonized with all seven IMDRF code sets. In addition, the FDA will accept IMDRF, FDA, and NCIT codes through the eMDR system.

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