Observational Health Data Sciences and Informatics

ICD9CM is a coding system based on WHO ICD9 codes, but containing multiple additions and modifications. Sources

• CMS: ICD-9-CM-vXX-master-descriptions.zip from http://www.cms.gov/Medicare/Coding/ICD9ProviderDiagnosticCodes/codes.html for billing codes
• UMLS: for non-billing codes

All Concepts are assigned the longest of all available names.

All ICD9CM codes are represented in the format containing the dot.

All ICD9CM codes are non-Standard.

ICD9CM Concept Classes identify each Concept as part of the general coding scheme of diagnoses and disorders, the codes for health status and contact with health services (V codes, starting with the letter “V”) and those for external causes of injury (E codes, starting with the letter “E”). 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 used for reimbursement of services, while non-billing codes are Chapter, Category or Sub Category codes.

Please refer to Concepts of ICD-9-CM for details of the composition of this vocabulary.

For each ICD9CM Concept, the Domain is inferred from the SNOMED Concept it is mapped to. If it is mapped to more than one concept, a combination Domain is assigned.

There are two types of relationships:

1. Direct ICD9CM to SNOMED maps recorded as “Maps to” relationships. These are manually curated based on input from UMLS (connection through common CUIs) and through MedDRA through ICD9CM to MedDRA maps in combination to MedDRA to SNOMED maps (see there). Pre-coordinated Concepts are mapped, if possible, to their components. For example, .
2. Maps for Concepts that do not represent entities at the time of recording. For example, Concepts for history of, family history of, need for vaccination, XXX etc. refer to observations that are made recorded at a certain time, but the medical entity they are referring to, such as the disease for which family history is recorded, belongs to a different point in time. These codes are mapped to SNOMED Observation Concepts using the “Maps to” relationship, and to the relevant medical entity to the “Maps to value” relationship.
3. Hierarchical relationships between 3, 4 and 5-digit Concepts. These are constructed for those Concepts where the shorter code is entirely subsumed by longer one. Note that these relationships also exist between 3 and 5-digit codes according to these rules, which deviates from the preferred convention that “Subsumes” and “Is a” relationships only exist between directly related Concepts.

ICD9CM Concepts are not Standard Concepts and therefore do not participate in the Hierarchy of the OMOP Standardized Vocabularies.