1. Introduction

1.1. Background

SNOMED CT terminology provides a common language that enables a consistent way of indexing, storing, retrieving, and aggregating clinical data across specialties and sites of care.

SNOMED International maintains the SNOMED CT technical design, the content architecture, the SNOMED CT content (includes the concepts table, the descriptions table, the relationships table, a history table, and ICD mappings), and related technical documentation.

1.2. Purpose

This document provides a summarized description of the content changes included in the December 2022 release of SNOMED Clinical Terms^® (SCT) International Release.

It also includes technical notes detailing the known content or technical issues where the root cause is understood, the fix has been discussed and agreed to, but has yet to be implemented.

The SNOMED International Release Notes are available alongside the December 2022 International release.

1.3. Scope

This document is written for the purpose described above and is not intended to provide details of the technical specifications for SNOMED CT or encompass every change made during the release.

1.4. Audience

The audience includes National Release Centers, WHO-FIC release centers, vendors of electronic health records, terminology developers and managers who wish to have an understanding of changes that have been incorporated into the December 2022 International release.

Please note, you may have to register for a Confluence user account in order to access the links included in these release notes.

2. Content Development Activity

2.1. Summary

Continuous quality improvement and enhancement of existing content is an ongoing process undertaken by SNOMED International in preparation for every release. The December 2022 International Release has seen a continuation of the work driven by contributions from: Kaiser Permanente i.e. Convergent Medical Terminology (CMT), Global Medical Device Nomenclature Agency (GMDNA), Orphanet and other domain specific collaborations as well as requests received via the Content Request System (CRS). 

Additionally quality improvement activities are advanced via project driven initiatives summarized below.  Additional work items impacting every release are updates to the SNOMED CT derived maps such as ICD-10 and ICD-O; details are included in these release notes.  

Information about editorial decisions may be found in the SNOMED CT Editorial Guide; mapping guidance for ICD-10 can be found here.

2.2. Quality Initiative

The Quality Initiative (QI) project is the implementation of the Quality Strategy. After a successful pilot project for the July 2018 release the next stage has been implemented for subsequent releases including December 2022. 

Quality improvement tasks are being deployed to improve internal structural consistency and ensure compliance with editorial policy related to the stated modeling of content. Additionally, correction or addition of defining relationships is being carried out to accurately reflect current clinical knowledge and ensure the semantic reliability of descriptions associated with a concept. 

2.2.1. Update to Model for 169952004|Placental finding (finding)| and 125586008|Disorder of placenta (disorder)|

169952004|Placental finding (finding)| and descendants and 125586008|Disorder of placenta (disorder)| have been remodeled with 125586008|Disorder of placenta (disorder)| now a descendant of 169952004|Placental finding (finding)|. Content in this area has been updated to include the attribute occurrence and an appropriate value, with improvements to the model for individual concepts and overall subsumption.

2.2.2. Pressure Ulcer and Pressure Injury

The descriptions and model of concepts across hierarchies including observable entity, procedure, situation with explicit context, where the term 'Pressure ulcer' is used in the descriptions, have been updated to align with the editorial guidance for pressure injury.

420226006 |Pressure ulcer (morphologic abnormality)| has been inactivated. ‘Pressure ulcer’ has been added as synonym to the pressure injury morphology concepts with the exception of stage 1. 

Work has been completed for the content tracker.

2.3. Body Structure 

2.3.1. Inactivation of 280928005|Structure of branch of retinal vein (body structure)|

280928005|Structure of branch of retinal vein (body structure)| is considered to be the same as 423404006|Structure of tributary of central retinal vein (body structure)|. The latter concept is preferred anatomically as the 'branches' often used clinically to define 'retinal branch vein thrombosis' are technically tributaries as the venous blood flows centrally into a common collecting vein - the central retinal vein.

2.3.2. Tendon Regions

Anatomical discrepancies between complete tendons that traverse more than one region, e.g. the lower leg, ankle, foot and toe, with segments of tendons limited within a defined region, have been rectified. For example there is a difference between the flexor hallucis longus tendon segment within the confines of the great toe and the complete tendon that courses through the foot from a more proximal origin. The impact of these changes allows disorders and procedures whose definitions are dependent on this anatomy to be classified more logically.

Where necessary additional tendon components have been added e.g. the four tendons of the triceps muscle have been added as separate concepts allowing the allocation of the exact tendon for the modeling of findings or procedures.

2.3.3. SEP and Laterality Anatomy Reference Sets

The release file for the lateralizable body structure reference set has been updated and validated.

The release file for the SEP reference set has been updated and validated.

2.4. Clinical Finding

2.4.1. Remodel of Concepts with Finding Site 9258009|Gravid uterus structure (body structure)|

Work has commenced to update content currently modeled with 9258009 |Gravid uterus structure (body structure)|.

• For the December 2022 release, over 100 concepts in the clinical finding hierarchy that were modeled with the site gravid uterus (<< 404684003 |Clinical finding (finding)| : * = (9258009 |Gravid uterus structure (body structure)| or 362253003 |Entire gravid uterus (body structure)|) have been reviewed.
• These concepts have been remodeled by using finding site of |Uterine structure| and occurrence |Maternal pregnancy period (qualifier value)|. The updated model addresses missing subsumption of conditions modeled by parts of the uterus during pregnancy.

Along with these changes, the following changes were also made:

• Update to the model of 198609003 |Complication of pregnancy, childbirth and/or puerperium (disorder)|. The incorrect model of maternal pregnancy period has been removed.
• Pregnancy finding and disorder concepts have been modeled with occurrence maternal pregnancy period and GCI axioms to include subconcepts that are modeled by a pregnancy observable.
• The model of some concepts has been improved by being fully defined with more specific observables, e.g. Finding of duration of uterine contraction (finding).
• The hierarchy of observable entity has been improved by assigning additional parent concepts.
• Clinical finding concepts relating to the pregnant abdomen have been modeled with the finding site of abdomen and occurrence maternal pregnancy period.

NOTE: Normal/abnormal findings of the gravid uterus and obstetric disorder of uterus are not complete though GCI axioms have identified some subtypes. Further review and improvement will continue in this content area.

2.4.2. Remodel Hierarchy 118245000|Measurement finding (finding)|

The following changes were made to the subtypes of 118245000|Measurement finding (finding)|

• Concepts which included 'high,' 'elevated,' 'raised,' 'low,' 'decreased,' normal,' etc. in the FSN had their FSN updated to 'above reference range,' 'below reference range,' or 'within reference range.' 
• Concepts which included 'abnormal' in the FSN had their FSN updated to include 'outside reference range.' The modeling of these concepts now includes 394844007 |Outside reference range (qualifier value)| as the value for Has interpretation (attribute).
• Concepts representing a finding about a therapeutic range were updated to include 'above therapeutic range,' 'below therapeutic range,' or 'within reference range' in the FSN. The Has interpretation (attribute) value of these concepts is now 281303003 |Above therapeutic range (qualifier value)|, 281306006 |Below therapeutic range (qualifier value)| or 281304009 |Within therapeutic range (qualifier value)| accordingly. 
• Concepts which included "borderline" in the FSN were inactivated as ambiguous.

2.4.3. Update for Subtypes of 363346000|Malignant neoplastic disease (disorder)|

Approximately 410 current 'agnostic' (ie. not specified as primary or metastatic) malignancy disorders that were previously only inferring a primary designation through their morphology hierarchy parent, have had a new primary malignancy concept added as a subtype that will be available for use in implementations as a subtype of 372087000 |Primary malignant neoplasm (disorder)|.

156 concepts that were previously 'agnostic' as to whether primary or metastatic, but carried maps to Orphanet codes as part of the ongoing collaboration, have been excluded from this release of new primary malignancy subtype concepts and are under review.

Concepts have also been excluded that are subtypes of: 269475001 |Malignant tumor of lymphoid, hemopoietic AND/OR related tissue (disorder)|.

2.4.4. Review of Synonyms in Hierarchy 363346000 |Malignant neoplastic disease (disorder)|

Approximately 65 new concepts have been added and provide a target value for inactivation of synonyms in cases where a primary malignancy synonym was found to be present on a concept that did not specify a primary malignancy disorder, and vice versa (a non-primary malignancy description was placed as a synonym on a primary malignancy disorder concept).

Concepts have been excluded that are linked to the Orphanet map and/or are subtypes of: 269475001 |Malignant tumor of lymphoid, hemopoietic AND/OR related tissue (disorder)|.

2.5. Qualifier Value

2.5.1. Inactivation of 272426002|Specific site descriptor (qualifier value)| and Subtypes

272426002|Specific site descriptor (qualifier value)| and subtypes contained a set of concepts that were mainly represented in the body structure hierarchy.  

Concepts such as 264010009|Gastric (qualifier value)| represented the adjectival form of the body structure. Some of these concepts duplicated descriptions for new concepts required for the drug maintenance project. 

For further information please see Briefing Note.

272426002|Specific site descriptor (qualifier value)| and subtypes have been inactivated with inactivation reason ‘non conformance to editorial policy’ and association ‘alternative’ with a target concept that is a subtype of 123037004|Body structure (body structure)| where appropriate.

2.6. Substance

2.7. Pharmaceutical/Biological Product

2.8. Physical Object

2.9. Collaboration/Harmonization Agreements

2.9.1. Convergent Medical Terminology (CMT)

The December 2022 release has seen a continuation of work for this project.

2.9.2. Orphanet

Working in collaboration with Orphanet (http://www.orpha.net/consor/cgi-bin/index.php), content development is ongoing for rare disease concepts in SNOMED CT. Content in scope for this project is published in the annual update of the SNOMED CT to Orphanet Maps.

All of the concepts added for the Orphanet project have been mapped to ICD-10.

2.9.3. ICD-11 Update

The December 2022 release has seen continued addition of content for this project.

2.9.4. Cancer Synoptic Reporting

Cancer synoptic reports are used by many member countries to record pathology examination of cancer specimens including the College of American Pathologists (US and Canada), Royal College of Pathology (UK), Royal College of Pathology Australasia (Australia, New Zealand), PALGA (The Netherlands), Swedish Society of Pathology, and others.

For more information about this project, please see Cancer Synoptic Reporting Clinical Project Group 

2.9.5. Social Determinants of Health - Gravity Project

6 new procedure concepts relating to microenterprise development programs and organizations have been added for the December 2022 release.

2.9.6. International League Against Epilepsy (ILAE)

In line with approved harmonised terminology, this project is working on alignment including restructuring to update the hierarchy  << 313307000 |Epileptic seizure (finding)|; the next scheduled publication of these changes will be in the February 2023 release.

Further information about the changes is available here. 

2.10. Internal Quality Improvement

2.10.1. Machine Readable Concept Model (MRCM) Changes

There have been no changes for the December 2022 release.

Changes that are in progress can be viewed via the MRCM Daily Build Browser

Please see early visibility notification for change to MRCM.

2.11. SNOMED CT derived products

2.11.1. ICD-10 map

The SNOMED CT to the International Statistical Classification of Diseases and Related Health Problems, Tenth Revision (© World Health Organization 1994) 2016 Version map (SNOMED CT to ICD-10 Map) is included in the SNOMED CT International release as a Baseline. The SNOMED CT to ICD-10 Map was created to support the epidemiological, statistical and administrative reporting needs of SNOMED International member countries and WHO Collaborating Centers.

The SNOMED CT to ICD-10 Map is released in Release Format 2 (RF2) only. It is located in the file der2_iisssccRefset_ExtendedMapFull_INT_20200731.txt, which is in the Map folder under Refset, in each of the three RF2 Release Type folders. 

The SNOMED CT to ICD-10 Map is released as Refset 447562003 |ICD-10 complex map reference set (foundation metadata concept)|.

2.11.2. Content Development Activity Summary

The map is a directed set of relationships from SNOMED CT source concepts to ICD-10 target classification codes.  The SNOMED CT source domains for the MAP are limited to subtypes of 404684003 |clinical finding|, 272379006 |event| and 243796009 |situation with explicit context|.  The target classification codes are ICD-10 2016 release. 

Mapped content for December 2022

The map provided for the December 2022 release has been updated, and now represents a complete map from SNOMED CT International release to ICD-10 2016 version.

• 848 newly authored concepts have been added and mapped.

• The SNOMED to ICD-O (morphology) map has no additional concepts added as a result of the ICD-O 3.2 review or added due to CRS requests. 

We would welcome feedback on any issues that users of the map may detect when using the map. Issues should be submitted via mapping@snomed.org

2.11.3. Technical Guide Exemplars

The Technical Guide Exemplars document has now been moved from the International Edition release package to a Confluence page.  This page can be found as part of the ICD-10 Mapping Technical Guide (see Appendix B), which is hosted here:  http://snomed.org/icd10map

2.11.4. SNOMED CT to OWL conversion and classification

The repository containing the toolkit enabling simple SNOMED CT to OWL conversion and classification can be found here, including documentation on its use: https://github.com/IHTSDO/snomed-owl-toolkit

Please contact SNOMED International at support@snomed.org if you would like to provide any feedback on ways to extend and improve the new toolkit.

3. Technical notes

3.1. Known Issues

Known Issues are content or technical issues where the root cause is understood, and the resolution has been discussed and agreed but has yet to be implemented.  This can be due to a number of reasons, from lack of time within the new monthly editing cycles, to the risk of impact to the stability of SNOMED CT if the fix were to be deployed at that stage in the Product lifecycle.  

For the current SNOMED CT International edition, the following Known Issues were identified, and agreed to be resolved in future editing cycles:

3.2. Resolved Issues

Resolved issues are Known Issues which were not fixed as part of the previous release lifecycle, but which have now been resolved in the latest release.  They can also be issues found during testing of the current release, which were resolved before the final deployment of the Production release.  Finally they can be issues which were reported or found during the testing phase, but which have been closed without any action taken.  

The Resolved Issues for the current SNOMED CT International edition can be found here:

3.3. Technical updates

3.3.1. RF2 package format

For future reference, the RF2 package convention dictates that it contains all relevant files, regardless of whether or not there is content to be included in each particular release.  Therefore, the package contains a mixture of files which contain both header rows and content data, and also files that are intentionally left blank (including only a header record).  The reason that these files are not removed from the package is to draw a clear distinction between files that:

• have been deprecated (and therefore removed from the package completely), due to the content no longer being relevant to RF2 in this or future releases, and 

• happen to contain no data in this particular release (and are therefore included in the package but left blank, with only a header record), but are still relevant to RF2, and could therefore potentially contain data in future releases.

This allows users to easily distinguish between files that have purposefully been removed or not, as otherwise if files in option 2 above were left out of the package it could be interpreted as an error, rather than an intentional lack of content in that release.

Configuration file in the RF2 package, containing Release Metadata 

A new file has been included since the July 2020 International Edition, containing metadata about the Release package itself.  This has been created in conjunction with feedback from the community, and as such initially contains the following fields:

• effectiveTime
  

• previouslyPublishedPackage

• languageRefset(s)

• licenceStatement

The file is in .JSON format, to ensure that it is both machine-readable and human-readable, and is named "release_package_information.json".

The metadata will be extended and refined going forward, in order to ensure that it contains the most useful information possible. If you have any ideas about any other useful information to include, please send them to info@snomed.org, along with a business case explaining how the information would benefit stakeholders.  Please be aware that this use case will then be assessed by SNOMED International, and the new metadata will only be included in the configuration file if the business case is strong enough.  

3.3.2. Early visibility of impending changes in the upcoming 2023 Monthly International Edition releases

Please see https://confluence.ihtsdotools.org/display/RMT/2023+Early+Visibility+Release+Notifications for details of forthcoming changes.