Vocab. MEDDRA
The Medical Dictionary for Regulatory Activities (MedDRA) is a clinically validated international medical terminology thesaurus and adverse event classification dictionary used by regulatory authorities and the biopharmaceutical industry during the regulatory process, from pre-marketing (clinical research phase 0 to phase 3) to post-marketing activities (pharmacovigilance or clinical research phase 4), and for safety information data entry, retrieval, evaluation, and presentation. Products covered by the scope of MedDRA include pharmaceuticals, biologics, vaccines and drug-device combination products.
The source data is provided by:
- MedDRA Website that is supported by the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH).
- MedDRA Support Documentation:
- MedDRA Term Selection: Points to Consider Release 4.21
- Redline of Changes to MedDRA Term Selection: Points to Consider Release 4.21
- MedDRA Data Retrieval and Presentation: Points to Consider Release 3.21
- Introductory Guide MedDRA Version 25.0
- Introductory Guide for Standardised MedDRA Queries (SMQs) Version 25.0
- Distribution File Format Version 25.0
- MedDRA Concept Description
- SNOMED CT MedDRA Simple Map Package
The procedures for transforming Concepts from the source to the OMOP Standard Vocabularies can be found on the OHDSI GitHub.
The MedDRA dictionary is organized with a five-level hierarchy. The highest or broadest level is System Organ Class (SOC), further divided into High-Level Group Terms (HLGT), High-Level Terms (HLT), Preferred Terms (PT) and finally into the most granular Lowest Level Terms (LLT).
Also, the MedDRA dictionary includes Standardised MedDRA Queries (SMQs). SMQs are groupings of terms that relate to a defined medical condition or area of interest.
MedDRA concepts have one distinct name per concept.
Concept codes are taken from the MedDRA codes (llt_code, pt_code, hlt_code, hlgt_code, soc_code from 1_low_level_term, 1_pref_term, 1_hlt_pref_term, 1_hltg_pref_term, 1_soc_term, respectively).
The majority of MedDRA concepts are in the “Condition” domain (counts: 07/2022).
| Domain | Count |
| Condition | 86011 |
| Measurement | 11685 |
| Procedure | 8307 |
| Observation | 2298 |
The MedDRA concepts are composed from the following Concept Classes.
| Class | Count | Notes |
| SOC | 27 | System Organ Class - the highest level of MedDRA hierarchy |
| HLGT | 352 | High-Level Group Terms |
| HLT | 1810 | High-Level Terms |
| PT | 25433 | Preferred Terms |
| LLT | 80679 | Lowest Level Terms |
MedDRA domain and concept classes were assigned pursuant to the following criteria:
| Source | Dependencies | Domain | Concept Class |
| MedDRA soc_term table | “soc_name” field value contains 'Investigations' | Measurement | SOC |
| soc_name field value contains IN ('Product issues', 'Social circumstances' ) | Observation | ||
| “soc_name” field value contains 'Surgical and medical procedures' | Procedure | ||
| “soc_name” field value contains 'disorders|Infections|Neoplasms|Injury, poisoning and procedural complications|Pregnancy, puerperium and perinatal conditions' | Condition | ||
| MedDRA hlgt_pref_term table |
“hlgt_name” field value contains 'Therapeutic and nontherapeutic effects
(excl toxicity)'
OR soc_name IN ( 'Product issues', 'Social circumstances') |
Observation | HLGT |
| “soc_name” field value contains 'disorders|Infections|Neoplasms|Injury, poisoning and procedural complications|Pregnancy, puerperium and perinatal conditions' | Condition | ||
| “soc_name” field value contains 'Surgical and medical procedures' | Procedure | ||
| “soc_name” field value contains 'Investigations' | Measurement | ||
| MedDRA hlt_pref_term table |
“hlt_name” field value contains 'exposures|Physical examination procedures
and organ system status'
OR “hlgt_name” field value contains 'Therapeutic and nontherapeutic effects (excl toxicity)' OR “soc_name” IN ('Product issues', 'Social circumstances') |
Observation | HLT |
|
“hlt_name” field value contains 'histopathology|imaging|procedure'
OR “soc_name” contains 'Surgical and medical procedures' |
Procedure | ||
|
“hlt_name” field value contains 'Gene mutations and other alterations NEC'
OR “soc_name” contains 'Investigations' |
'Measurement' | ||
| “soc_name” field value contains 'disorders|Infections|Neoplasms|Injury, poisoning and procedural complications|Pregnancy, puerperium and perinatal conditions' | Condition | ||
| MedDRA pref_term table |
“pt_name” field value contains 'monitoring|centesis|imaging|screen'
OR “hlt_name” contains 'histopathology|imaging|procedure' OR “soc_name” contains 'Surgical and medical procedures' |
Procedure | PT |
|
“hlt_name” field value contains 'exposures|Physical examination procedures
and organ system status'
OR “hlgt_name” contains 'Therapeutic and nontherapeutic effects (excl toxicity)' OR “soc_name” IN ('Product issues', 'Social circumstances' ) |
Observation | ||
|
“hlt_name” field value contains 'Gene mutations and other alterations NEC'
OR “soc_name” contains 'Investigations' |
Measurement | ||
| “soc_name” field contains 'disorders|Infections|Neoplasms|Injury, poisoning and procedural complications|Pregnancy, puerperium and perinatal conditions' | Condition | ||
| MedDRA low_level_term table | “soc_name” field value contains 'disorders|Infections|Neoplasms|Injury, poisoning and procedural complications|Pregnancy, puerperium and perinatal conditions' | Condition | LLT |
| “pt_name” field value contains:
'Monitoring|centesis|imaging|screen' OR “hlt_name” contains 'histopathology|imaging|procedure' OR “soc_name” contains 'Surgical and medical procedures' |
Procedure | ||
|
“hlt_name” field value contains 'exposures|Physical examination procedures
and organ system status'
OR “hlgt_name” contains 'Therapeutic and nontherapeutic effects (excl toxicity)' OR “soc_name” IN ('Product issues', 'Social circumstances') |
Observation | ||
|
“hlt_name” field value contains 'Gene mutations and other alterations NEC'
OR “soc_name” contains 'Investigations' |
Measurement |
Relationships are defined within MedDRA and between MedDRA and SNOMED.
A purpose of Internal MedDRA relationships is to build a MedDRA Hierarchy, which makes it easier to sort and browse the database for flexible data retrieval and for the clear presentation of data. The five-level structure of this terminology provides options for retrieving data by specific or broad groupings, according to the level of specificity required. The Lowest Level Term (LLT) level provides maximum specificity.
| Relationship (reverse relationship) | From | To | Count |
| Is a | Descendant MedDRA Class | Ancestor MedDRA Class | 90521 |
| Subsumes | Ancestor MedDRA Class | Descendant MedDRA Class | 99001 |
| MedDRA contained in SMQ (MedDRA) (SMQ consists of MedDRA (MedDRA)) |
MedDRA | SMQ | 16633 |
Most MedDRA concepts are Classifications or non-Standard concepts which means that they are mapped to the respective Standard concepts defined by the vocabulary team. Technically, they have single (1-to-1) or several (1-to-many) “Maps to” relationships in the concept_relationship_table. The purpose of External MedDRA relationships to SNOMED is to map them with Standard concepts (such as SNOMED) and use them for analysis in OHDSI models. In July 2022 all possible ‘MedDRA-SNOMED eq’ were replaced by valid ‘Maps to / Maps to value’ SNOMED mapping.
Current external MedDRA relationships:
| Relationship | Count |
| Maps to | 13599 |
| Maps to value | 840 |
| MedDRA-HOI (health outcomes of interest) | 363 |
Most MedDRA concepts are Classifications or non-Standard concepts. That means they have to be mapped to the corresponding Standard Concepts using the CONCEPT_RELATIONSHIP table ("Maps to" and occasionally "Maps to value" records). Most of them are mapped to single SNOMED Concepts, generating one-to-one records in the CONCEPT_RELATIONSHIP table, but some of them create multiple records or have mappings to other domains.