Vocab. ICD10CM

ICD10CM

ICD10CM, often spelled “ICD-10-CM”, is a coding system in the USA, which is based on the WHO ICD10 coding system, but contains a large number of additions and extensions:

• Laterality of conditions
• Initial encounter, subsequent encounter with the healthcare system
• Routine healing and delayed healing information
• More detail for injuries and external causes of injuries

Note: ICD10CM is often simply referred to as “ICD-10” in the literature, creating confusion with the WHO ICD10. Many of the codes are equivalent, but because of the modifications and additions it is a vocabulary in its own right in the OMOP Standardized Vocabularies. For a discussion of the WHO ICD10 please visit here.

Sources

• https://www.cdc.gov/nchs/icd/icd10cm.htm

Transformation

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 ICD10CM codes are represented in the format containing the dot.

Standard Concepts

All ICD10-CM 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.

Domains

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

Domain	Notes
Condition	bulk of concepts
Condition/Device
Condition/Meas
Measurement
Observation	second largest number of concepts
Procedure

Concept Classes

ICD10CM Concept Classes identify each Concept as part of the general coding scheme of diagnoses and disorders, classified into 21 Chapters (not explicitely identified in the OMOP Standardized Vocabularies). In addition, the Concept Classes distinguish between billing and non-billing codes. These are defined according to the Health Care Services Coding System of the Centers of Medicare and Medicaid Services (CMS). Billing codes are those that are designated for reimbursement of services, while higher level codes are non-billing.

Class	Notes
3-char nonbill code
3-char billing code
4-char nonbill code
4-char billing code
5-char nonbill code
5-char billing code
6-char nonbill code
6-char billing code
7-char billing code	There are no 7-character non-billing codes

Concept Relationships

There are only mapping relationships defined for ICD10.

ICD10CM to SNOMED map

ICD10CM 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 ICD10CM 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.

Hierarchy

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

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.