The Need for a Unified Terminology
Before MedDRA's development in the late 1990s by the International Council for Harmonisation (ICH), various disparate terminologies were used across the globe for coding and reporting adverse events. This fragmentation led to inconsistencies in data capture and reporting, making international analysis and comparison of drug safety data extremely difficult and inefficient. The establishment of a single, highly specific, and internationally applicable terminology was a significant step towards improving global patient health by allowing for better electronic exchange of safety information.
The Hierarchical Structure of MedDRA
The MedDRA terminology is organized into a robust, five-level hierarchy that allows for varying levels of specificity in data retrieval and analysis.
- System Organ Class (SOC): The highest, broadest level, grouping terms by organ system, etiology, or purpose. There are 27 non-exclusive SOCs.
- High-Level Group Term (HLGT): Groups of clinically related High-Level Terms within an SOC.
- High-Level Term (HLT): Subgroups of related Preferred Terms.
- Preferred Term (PT): A unique, single medical concept for coding and reporting. This is the standard level for data analysis output.
- Lowest Level Term (LLT): The most granular level, including synonyms, lexical variants, and abbreviations of a Preferred Term. LLTs are used for data entry.
This hierarchical, multiaxial structure ensures consistency and flexibility. A single medical event can be linked to multiple SOCs, which is crucial for analyzing complex clinical manifestations that affect several organ systems.
Role in Pharmacovigilance and Safety Monitoring
MedDRA is a foundational tool for pharmacovigilance, the science and activities related to the detection, assessment, understanding, and prevention of adverse effects or any other drug-related problem. The standardization MedDRA provides is critical throughout a drug's lifecycle, from clinical trials to post-market surveillance.
Key functions within pharmacovigilance include:
- Standardized Adverse Event Reporting: MedDRA provides a consistent language for coding adverse events (AEs) and adverse drug reactions (ADRs), eliminating ambiguities from verbatim reports.
- Signal Detection: The hierarchical structure and specialized tools like Standardised MedDRA Queries (SMQs) help in detecting safety signals. SMQs are validated, expert-defined groupings of terms that facilitate the investigation of specific medical conditions or areas of interest across large datasets.
- Data Integration: By using a common terminology, MedDRA allows for the seamless integration and pooling of safety data from various sources and studies, providing a comprehensive view of a product's safety profile.
MedDRA in Regulatory Submissions
Regulatory authorities globally, such as the FDA in the U.S., the European Medicines Agency (EMA), and Health Canada, mandate or prefer the use of MedDRA for submissions. This requirement ensures that regulatory information is structured consistently, regardless of the company or country of origin. MedDRA is integral to the Electronic Common Technical Document (eCTD), the standardized format for regulatory submissions, and Individual Case Safety Reports (ICSRs).
Comparative Analysis: MedDRA vs. Other Terminologies
While MedDRA is a dominant force in regulatory reporting, other medical terminologies exist for different purposes. A comparison highlights the distinct function of MedDRA.
| Feature | MedDRA | ICD (International Classification of Diseases) | SNOMED CT (Systematized Nomenclature of Medicine—Clinical Terms) |
|---|---|---|---|
| Primary Purpose | Regulatory reporting and pharmacovigilance for medical product safety. | Classification of diseases, symptoms, and health conditions for clinical and billing purposes. | Comprehensive clinical reference terminology for use in electronic health records. |
| Granularity | Highly specific, with detailed Lowest Level Terms for coding individual events. | Broader, designed for disease and health condition classification rather than specific adverse events. | Extremely comprehensive and detailed for clinical documentation. |
| Structure | Multiaxial, five-level hierarchy allowing terms to appear in more than one organ class. | Monohierarchical structure. | Complex, polyhierarchical structure. |
Ongoing Maintenance and Governance
MedDRA is not a static dictionary but a constantly evolving terminology. Its maintenance, development, and distribution are managed by the Maintenance and Support Services Organization (MSSO), under the oversight of the ICH MedDRA Management Committee. The MSSO releases updated versions of MedDRA biannually to ensure the terminology remains current with new medical knowledge and user needs. This robust governance and update process is crucial for maintaining the integrity and relevance of MedDRA as a global standard.
Conclusion: The Impact of a Standard Language
Ultimately, the purpose of MedDRA is to serve as the critical infrastructure for standardized medical communication in the regulatory and safety arenas. By providing a consistent, detailed, and flexible language for adverse event reporting, MedDRA allows stakeholders to enter, retrieve, and analyze safety data more effectively. This harmonization across the product lifecycle enhances the detection of potential safety issues and facilitates the electronic exchange of crucial information. In doing so, MedDRA plays a direct and vital role in improving the global protection of patient health. For more information, the official MedDRA website provides extensive resources and documentation.
