Version 2.83, October 2026

This release is compliant with the SNOMED CT RF2 specification and contains a complete set of full and snapshot release files. The production content is released in the 11010000107 |LOINC Extension module|, aligned with the 2026-07-01 version of the International release of SNOMED CT, and Version 2.83 of LOINC, released 2026-08-24.

This release contains over 46,000 SNOMED CT concepts representing active and discouraged laboratory LOINC Terms. Among the most frequently used LOINC concepts, coverage for this release of the LOINC Ontology includes:

Change in project home

The home for the LOINC Ontology has moved from loincsnomed.org to loinc.org/ontology. This location will hold downloads, links to the browser, and documentation. The former URL will redirect to the new location indefinitely. The change is being made to ease maintenance and support.

Modeling updates

We are continuing to advance laboratory observables within the LOINC Ontology by introducing new concepts and refining existing models to enhance data quality, accuracy, and data exchange and interoperability.

Key updates include

  • Microbiology Post-Coordination Expansion: We added 500 new genetic microbiology concepts and updated 50 existing microbiology concepts to allow post coordination of specimen type and method when testing for the presence of microbiology RNA and DNA. These concepts all have a System of “{ Specimen}” and a Method of ‘{Molgen}” to indicate the information about the tests (the specimen type and the kind of genetic method) that is to be post-coordinated in the results.
  • Drug & Toxicology Restructuring: Added ~500 new Drug/Tox concepts as part of an ongoing class optimization. Generic “screening” or “confirmation” designations in the Method attribute were replaced with precise analytical methods (e.g., Immunoassay, Mass Spectrometry) or left methodless where appropriate to accurately reflect clinical testing practices.
  • Gene Mutation Standardization: Refactored gene mutation concept representations by isolating the gene mutation component and standardizing the Method attribute to Targeted gene mutation analysis, aligning our modeling approach with SNOMED CT.
  • Microbiology Property Alignment: Updated the Property attribute from Prid (Presence) to PrThr (Presence Threshold) across the Microbiology class to correctly represent qualitative and ordered categorical results.

Known issues in this LOINC Ontology release

  • Phrases that are not compliant with rules for proper descriptions in SNOMED CT, e.g., “non-prob.amp.tar”.
  • LOINC Terms defined by LOINC Part (LP) “Antibiotic XXX” (‘other antibiotic’).
  • LOINC Terms modeled as process observables where the Component value is mapped to a SNOMED CT calculation, e.g., 104805-7|Creatinine renal clearance predicted.
  • Some fully specified names (FSNs) contain inconsistencies based on the terming of the SNOMED CT attribute value concepts.
  • The FSN of LOINC concepts when the concept has a divisor and an adjustment, e.g., 30905-4|Cobalamin (Vitamin B12) [Ratio] in 24 hour Urine –post dose cyanocobalamin+intrinsic factor/post dose cyanocobalamin.
  • There is no connection between a LOINC panel and its constituents.
  • There is no connection between nominal LOINC concepts and their Answer Lists.
  • Supersystems are not semantically represented.
  • Descriptions of LOINC challenge concepts are not fully defined.

Validation Issues

The following validation issues have been identified in the version 2.82 of the LOINC Ontology. While these are valid problems according to SNOMED International validation tools, they were assessed as unlikely to present a material issue for implementers or to pose any adverse impact in clinical settings.

  • Duplicate FSNs between active and inactive content

    FSNs are required to be unique in active content in SNOMED CT, and even with inactive concepts, SNOMED International would normally reactivate a previously retired concept rather than create a new one with the same FSN. However, in the case of the LOINC Ontology, the link between LOINC Nums and SCTIDs in the alternate identifier table means that we may see the same FSN being generated when a LOINC concept has been replaced by another LOINC concept that uses the same parts. We cannot reuse a pre-existing concept because the LOINC Num remains bound to it for all time–even when both the LOINC concept and the SNOMED concept have been inactivated.

  • Invalid characters

    A few FSNs were flagged for use of a hash symbol (#) or ampersand (&), which is contrary to SNOMED International Editorial Policy. For example:

    CodeSCTIDFSN
    53273-9590721010000104Urinalysis type of non-squamous epithelial cells panel [#/volume] – Urine by Computer assisted method (observable entity)
    50184-171841010000104Mass concentration of calcitonin in serum or plasma at point in time pre 2 mg/kg calcium & 0.5 ug/kg pentagastrin IV (observable entity)

    Additionally, some synonyms were reported as containing one or more characters @, $, # or (). The LOINC Long Common Name is used directly as the FSN for panels, and is therefore not subject to SNOMED Editorial policy.

  • Non-compliance to Machine Readable Concept Model (MRCM) specifications

    Since the LOINC Extension is produced using a template based transformation of officially published LOINC concepts, the LOINC Ontology team (representing both SNOMED International and Regenstrief Institute) is not concerned that modeling will be introduced that will ultimately contravene the SNOMED International Machine Readable Concept Model (MRCM). A number of modeling questions have been raised through this collaboration, and each time this has resulted in an expansion of the MRCM to allow for a wider range of expression. We have not yet experienced any situation where an MRCM restriction has been found to indicate a content problem, or require a change to the LOINC Ontology.

    MRCM validation checks report a small number of model contraventions – particularly in the area of cardinality (i.e., rules about how many of each attribute can appear in a concept), which we expect to have resolved by the time the next release is published.

  • Case significance validation

    In general, LOINC is less prescriptive about case significance than SNOMED CT. SNOMED CT has a policy of capitalizing descriptions and providing a separate indicator to say if this capital can safely be made lower case. There are concepts in LOINC where descriptions deliberately start with a lower case character when Tall man lettering is being used, for example in 614921010000103 |fentaNYL and Norfentanyl panel – Serum or Plasma (observable entity)|.

    Additional validation issues arise from the use of “initial character case insensitive” in SNOMED CT, which has no representation in LOINC. This has resulted in warnings that the guidance that “Active terms sharing first word with case-sensitive term should share case sensitivity” has not been followed.