Observational Health Data Sciences and Informatics

All elements in the Vocabularies have a representation as a Concept in the CONCEPT table. This results in three categories of Concepts:

• Standard Concepts: A Standard Concept is the “official” Concept that is to be used to represent a unique clinical entity. They are designated as such in the field standard_concept = 'S'. Only Standard Concepts can appear in the *_concept_id or *_type_concept_id fields of the Standardized Clinical Data Tables of the CDM.
• Classification Concepts (designated in standard_concept = 'C') have a hierarchical relationship to Standard Concepts and can therefore be used to query for Standard Concepts using the records of the CONCEPT_ANCESTOR table. However, they themselves cannot appear in the Data Tables. For example, the Concept 4283987 “ANTICOAGULANTS” of the Vocabulary “VA Class” cannot appear in the DRUG_EXPOSURE or DRUG_ERA tables, but its Descendant Concepts that have the Concept Class “Ingredient”, “Clinical Drug” or “Branded Drug” can.
• Source Concepts can only appear in the *_source_concept_id fields of the Data Tables. They represent the code in the source data. Each Source Concept is mapped to one or more Standard Concepts during the ETL process. If no mapping is available, the Standard Concept with the concept_id = 0 is written into the *_concept_id field. See Data ETL Section for details.

The designation of a Concept as Standard, Classification or Source depends on the Vocabulary. See the specifications for each Vocabulary for details.