The Medical Dictionary for Regulatory Activities (MedDRA) was developed through the International Conference on Harmonisation (ICH) of Technical Requirements for Registration of Pharmaceuticals for Human use with the purpose of creating an “internationally accepted terminology for biopharmaceutical regulatory purposes” (1) and to make easier the management of the information required for product registration and data cross-reference. Its first official version (2.0) was released in July 1997.
“The MedDRA terminology applies to all phases of development of medical products for human use, excluding animal toxicology. The scope of MedDRA encompasses medical, health-related and regulatory concepts pertaining to such products. The terminology also addresses the health effects and malfunction of devices.”
The building of the terminology is based in a hierarchical structure that includes (from lowest to highest):
– **Lowest Level Term (LLT)**: Each one of these terms is linked to only one Preferred Term (PT) and it could function as a synonym, as a lexical variant, as a quasi-synonym, and as a sub-element of their parent PT, in some cases an LLT is identical to its PT for data entry purposes. “There is no limit to the number of LLTs that can be linked to a Preferred Term.”
– **Preferred Term**: Is a single medical concept for specific symptoms, signs, diseases, diagnoses, therapeutic indications, etc. “A PT must have at least one LLT linked to it.”
– **High Level Term (HLT)**: Are categories containing the PTs by anatomy, pathology, physiology, etiology or function.
– **High Level Group (HLG)**: Are descriptors for HLTs related by anatomy, pathology, physiology, etiology or function.
– **System Organ Class (SOC)**: Is the highest level and groups by etiology, manifestation site and purpose.
LLTs “may accommodate to colloquial or culturally unique terms” , facilitate the transfer of historical data, data entry, consistency and auto-encoding. They are more specific than PTs. LLTs that carry a “non-current” flag status are very vague, ambiguous, truncated, abbreviated, out-dated or misspelled (this dataset does not indicates LLTs flags).
The abbreviations in MedDRA are for LLT level, except when the full term surpasses the 100 characters and when the term has a well-established abbreviation. These exceptions include:
– CDC: Centers for Disease Control (USA)
– CNS: Central Nervous System
– CSF: Cerebrospinal fluid
– ECG: Electrocardiogram
Other exceptions to the norm are:
– NEC: Not Elsewhere Classified. It is limited to HLT and HLGT levels.
– NOS: not other specified. Limited to the LLT level.
The majority of abbreviated virus such as LLT HAV, LLT HBV and LLT Hepatitis B virus, are non-current.
“Chemical elements are represented in MedDRA with their official chemical symbols.”