6.6.1 Document Ontology artifact

Beginning with LOINC version 2.44 (June 2013), a delimited text file containing the relationships between clinical document terms (i.e. those within the Class of DOC.ONTOLOGY) and their associated ontology axis values is available for download as part of the LOINC distrubtion. The DocumentOntology.csv file is located within the AccessoryFiles folder.

The document ontology axis values have been assigned LOINC Part identifiers and classified according to their document ontology axis. This file defines the relationships between a given LOINC term and its ontology axis values through these fields: LoincNumber, PartNumber, PartTypeName, PartSequenceOrder, PartName. These fields are largely self-explanatory, but of note is that the PartTypeName corresponds to the Document Ontology axis, and the PartSequenceOrder is relevant for terms that combine axis values from within an axis (see Section 7.4).

6.6.2 Document Ontology in OWL format

Beginning with LOINC version 2.68, a computable format of the LOINC document ontology hierarchies and the relationships of all ontology parts to LOINC terms has been available in a Web Ontology Language (OWL) format. The DocumentOntology.owl file is located within the AccessoryFiles folder of the LOINC distribution.

This format of the LOINC Document Ontology is in development and has an Alpha maturity status.

6.6.2.1 About OWL

OWL is a file format that stands for “Web Ontology Language”. In general, knowledge expressed in OWL format is computer-readable and can represent rich knowledge about resources (such as LOINC Parts and LOINC terms) and the relationships between them. Since OWL is a standard format for representing ontological information, it is possible to query that knowledge, build visual representations, and make inferences if you have the right tools.

For further information about OWL and ontology, we recommend resources available from The University of Manchester and the World Wide Web Consortium.

The LOINC DocumentOntology.owl file can be viewed using an ontology editing and browsing tool such as the open-source Protégé platform from Stanford University. Users who are familiar with such ontology tools should be able to run queries, and view inferences about the relationships between the individual LOINC document concepts.

Protégé hierarchy view of LOINC Document Ontology

Protégé visualization of a Subject Matter Domain within the LOINC Document Ontology

Protégé visualization of a single document within the LOINC Document Ontology

6.6.3 Other locations of Document Ontology content

  • A visual representation of the current LOINC Document Ontology by axis values is located in Section 6.4 of this documentation.
  • A value set containing LOINC Document Ontology codes is available programmatically from the LOINC Terminology Service using HL7 FHIR. The URI for this value set is http://loinc.org/vs/loinc-document-ontology.
  • The Document Ontology can be viewed using LOINC’s web-based Hierarchy Browser. Select it from the hierarchy drop-down menu options.
  • LOINC document codes can be queried from the web-based SearchLOINC tool. In addition to finding document codes by name (e.g, progress note), you can use the following syntax to return all document ontology codes, class:DOC.ONTOLOGY. You can combine these approaches to find documents named progress note and with the appropriate class.
  • The above search queries and syntax can also be used programmatically with our Search API.