UMLS
The Unified Medical Language System, the US National Library of Medicine’s integration of many source vocabularies under shared concept identifiers.1 OIDM uses it for two jobs.
The first is crosswalking. The molu lookup tool resolves a concept to its UMLS concept unique identifiers and then translates to codes in other vocabularies; the stated design makes “UMLS as the CUI hub” part of the default radiology profile, alongside RadLex, LOINC, SNOMED CT, and FMA.23 The roadmap is explicit that a crosswalk is not an equivalence: translation should preserve “mapping direction, scope, provenance, and strength instead of treating every cross-reference as equivalence.”2
The second is as a cross-reference code on anatomic locations, present on 578 of the 2,890 records in the curated set.4
Synonyms and near-synonyms
- CUI, a concept unique identifier, is one UMLS identifier, not the system.
- UTS, the UMLS Terminology Services, is the REST API the lookup tool calls.
- Metathesaurus is the UMLS component that holds the source vocabularies.
- Index code with
system: "UMLS"is how a UMLS reference appears in OIDM data.
Identifier form
C followed by seven digits, for example C0001575.
Where it is used
Ontologies used, med-ontology-lookup, and Data model.
Conflicts
UMLS requires a licence and an API key, so any OIDM tooling that depends on it fails differently for an unlicensed caller. The lookup tool’s typed failure model exists partly for this reason, separating absence of a result from authentication, authorization, and licensing failures so the latter stay visible rather than silently falling back.3 A tracked issue also records that co-occurring CUI ambiguity is currently lost rather than preserved.