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  1. Mandatory Reporting Requirements: Manufacturers, Importers and Device User Facilities

MDR Adverse Event Codes

The FDA Medical Device Report (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 seven separate categories, each of which is organized hierarchically. In addition, the FDA MDR adverse event codes are mapped to two other coding systems: the National Cancer Institute Thesaurus (NCIt) and the International Medical Device Regulators Forum (IMDRF) Adverse Event Reporting terminologies. This page contains information about the codes and the MedWatch Medical Device Reporting Code Instructions, sometimes referred to as the coding manual.

Code Types

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

Code Type Purpose: These Terms/Codes Describe…
Medical Device Problem Problems (malfunction, deterioration of function, failure) of medical devices
Medical Device Component The parts and components which were involved in, or affected by, the medical device adverse event/incident.
Cause Investigation - Type of Investigation What was investigated and what kind of investigation was conducted to specify the root cause of the adverse event.
Cause Investigation - Investigation Findings The findings in the specific investigation that are the keys to identify the root cause of the event.
Cause Investigation - Investigation Conclusion The conclusion regarding the root cause of the reported event.
Health Effects - Clinical Signs and Symptoms or Conditions The clinical signs and symptoms or conditions of the affected person appearing as a result of the medical device adverse event/incident.
Health Effects - Health Impact The consequences of the medical device adverse event/incident on the person affected.

Note: Certain codes may be referred to by various names. For example, “device codes” refers to Medical Device Problem and Medical Device Component, “patient codes” refers to the two Health Effect sets, and “evaluation codes” refers to the three Cause Investigation sets. Device Problem Code and Patient Problem Code are often referred to collectively as Event Problem Codes, due to the label on section F10 of a previous version 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 a previous version 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 a participant in the IMDRF Adverse Event Terminology working group, which aims to improve and harmonize medical device adverse event coding among participating regulatory agencies. This working group maintains a guidance document with seven annexes containing the IMDRF codes, which are posted to the IMDRF documents repository.

The FDA is fully harmonized with IMDRF, so each FDA code is mapped to a single corresponding IMDRF code. Electronic MDR reporters may use IMDRF codes when entering adverse event codes into the FDA Form 3500A XML document, in addition to FDA or NCIt codes.

As a result of this harmonization effort, the FDA is no longer adding new adverse event codes in response to manufacturer requests. Manufacturers and other stakeholders who would like to request to add a new adverse event code should follow the IMDRF code request process. The FDA adverse event codes will be updated regularly in harmony with the IMDRF maintenance process, which typically occurs at least once per year.

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