Regenstrief InstituteSNOMED International

LOINC Ontology Technical Release Notes

Note: the LOINC Ontology version name 2.82 reflects alignment with the corresponding LOINC release cycle (LOINC 2.82, released February 24, 2026), rather than implying a separate major revision.

Version 2.82, March 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 2026-01-01 version of the International release of SNOMED CT, and Version 2.82 of LOINC, released 2026-02-24.

This release contains over 45,000 SNOMED CT concepts representing both active and discouraged laboratory LOINC Terms. In terms of coverage of the most used LOINC concepts, this release of the LOINC Ontology features:

Modeling updates

  • Coagulation tests
    The representation of coagulation tests, including clotting times, platelet aggregation, clotting factor assays, and clotting factor activities was revised. The main change for these items was moving method/technique information about coagulation induction, additives, dilutions, etc. from the Component field to the Method field.

  • Susceptibility tests
    We revised the representation of antibiotic susceptibility tests that had a specified concentration for testing. We moved the concentration of the antibiotic used in the test to be information in the Method field. For example, “Amikacin 12.0 ug/mL Susc Pt Isolate OrdQn Method for Slow-growing mycobacteria” was revised to say “Amikacin Susc Pt Isolate OrdQn Method for Slow-growing mycobacteria.antibiotic concentration at 12.0 ug/mL”.

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: [INDENT THE TABLE]

Code SCTID FSN
53273-9 590721010000104 Urinalysis type of non-squamous epithelial cells panel [#/volume] – Urine by Computer assisted method (observable entity)
50184-1 71841010000104 Mass 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.

  • Descriptions exceeding 255 characters
    Fully specified names (FSNs) in the LOINC Ontology are determined programmatically by assigning attribute values to slots in a template. Because of this, LOINC concepts that use individual parts with long names can combine to form an FSN with more than the current limit of 255 characters. SNOMED International has given notice that it intends to extend this character limit, and so systems designed to work with the LOINC Ontology (and SNOMED CT in general) are encouraged not to “hard code” field size limits for descriptions. For example, LOINC 48643-1 / SCTID 562611010000103.

  • 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.