LOINC has traditionally represented clinical observations through pre-coordinated terms, in which the information needed to describe an observation is represented within a single LOINC term. This approach remains important and continues to support implementations around the world.
As health information becomes more detailed, and as the ways in which data are exchanged and reused continue to evolve, there is a growing need for greater flexibility in how certain clinical information is represented. To support these evolving needs, LOINC is expanding its content and guidance to enable post-coordinated representations where appropriate.
Post-coordination allows a primary LOINC term to represent the core clinical observation, while additional information — such as method, specimen characteristics, body position, thresholds, or other qualifying details — is represented separately using standardized attributes and values. This provides another way for implementers to represent detailed clinical information without requiring every possible combination of characteristics to be expressed through a distinct LOINC term.
The addition of post-coordination support is intended to complement, rather than replace, LOINC’s established pre-coordinated approach. Existing pre-coordinated terms continue to be supported, and appropriate requests for new pre-coordinated terms are still accepted. Post-coordination is an additional capability that can help meet emerging interoperability and implementation needs.
This section describes why LOINC is supporting post-coordination, how LOINC models the values that a post-coordinated axis can resolve to, and what implementers should do today. The naming notation that flags a post-coordinated axis value is described in Section 2.1.8.
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