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ICD10 (often spelled “ICD-10”) is a coding system developed by the WHO for the purpose of disease and mortality reporting.

Note: In some countries, ICD10 is extended by local codes. For example, in the US a derivative system called ICD10CM is in use, in Germany a similar ICD10GM. Even though many of the codes are shared, those country-specific coding systems are separate and distinct vocabularies in their own right in the OMOP Standardized Vocabularies.



The procedures for transforming Concepts from the source to the OMOP Standard Vocabularies can be found on the OHDSI GitHub.

Concept Names

All Concepts are assigned the longest of all available names.

Concept Code

All ICD10 codes are represented in the format containing the dot.

Standard Concepts

All ICD10 codes are non-Standard 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.

Concept Classes

ICD10 has two Concept Classes: “ICD10 code” and “ICD10 Hierarchy”. “ICD10 Hierarchy” Concepts are all highest level 3-character codes. All codes which are subclassifications of them and contain a dot in the code are Concept Class “ICD10 code”.


For each ICD10 Concept, the Domain is inferred from the SNOMED Concept it is mapped to. If a ICD10 Source Concept is mapped to more than one target SNOMED Concept, a combination Domain is assigned. If a ICD10 Concept has no mappings the Domain is inferred from its neighboring codes.

ConditionBulk of ICD9CM codes

Concept Relationships

There are only mapping relationships defined for ICD10.

ICD10 to SNOMED map

ICD10 concepts are non-Standard Concepts and therefore are mapped to Standard Concepts through records in the CONCEPT_RELATIONSHIP table. All such mappings point to SNOMED-based concepts. Most of these SNOMED Concepts are in the Condition Domain, but despite the fact that ICD10 is a “Classification of Disease” some of them get mapped to Procedure, Measurement and Observation Domain Concepts. All mappings are manually maintained by a team of curators.

Most mappings establish one-to-one equivalence between the Concepts. However, some ICD10 Concepts are pre-coordinated (consist of several semantic components), contain negations, declarations about conditions at an unspecified time in the past (e.g. medical history of), declarations about people other than the patient (e.g. family history), lab test findings, mixed mother/child conditions or Observations. All these cases are properly handled as described in the Mapping description.

Instructions for ETL

All ICD10 concepts are non-Standard. 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 Condition Concepts, generating one-to-one records in the CONDITION_OCCURRENCE table, but some of them create multiple records or mappings to other domains.


ICD10 Concepts are non-Standard Concepts and therefore do not participate in the hierarchy of the CONCEPT_ANCESTOR table.

documentation/vocabulary/icd10.txt · Last modified: 2020/08/19 08:12 by ptalapova