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 January 2024 release of SNOMED Clinical Terms^® (SCT) International Edition.

It also includes 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 January 2024 International Edition.

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.

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 January 2024 International Edition.

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

1.5. Important Information

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 January 2024 International Edition 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 Edition the next stage has been implemented for subsequent releases including January 2024. 

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 Descriptions for Urinary Bladder

Following feedback from translation users, descriptions for concepts that contain the word 'bladder' and the site of 89837001|Urinary bladder structure (body structure)| have been updated to include 'urinary' in the FSN and PT, for example:

• 126885006|Neoplasm of bladder (disorder) has been updated to
• 126885006|Neoplasm of urinary bladder (disorder).

Number of concepts edited (approx): 1000

2.2.2. Update Breast Prosthesis Procedure Concepts

Procedure concepts relating to breast prosthesis have been updated with Method = 129338005 |Surgical implantation - action (qualifier value)| to align with naming of prosthesis implant.

Number of concepts edited (approx): 12

2.2.3. Transplantation Procedure

77930002 |Transplantation of artery (procedure)| and 10 subtypes and 119820001 |Vein transplantation (procedure)| and 1 subtype concept have been inactivated based on expert advice that these procedures relate to arterial bypass grafts or interposition grafts and the concepts were therefore ambiguous.

2.3.  Body Structure 

2.3.1.  Revision of Thorax

The new concept model for revision of the thorax has resolved missing relationships.

Key changes include:

• Thoracic vertebral column region is part of the upper back.
• Posterior chest wall is part of the posterolateral chest wall and the back of thoracic region.
• Posterolateral chest wall is part of the chest wall, and it is a union of two regional parts: the posterior chest wall, and the lateral chest wall.
• Areas of cardiac auscultation have been moved to subtypes of the anterior chest wall.
• The mammary region is part of pectoral region.
• Skin structure of upper back is part of skin structure of upper trunk.

Number of concepts edited (approx): 36

2.3.2. Revision of Thoracic Cage

The thoracic cage, also known as the rib cage, consists of 12 pairs of ribs and associated costal cartilages, as well as the sternum. However, Gray's Anatomy and other sources include the 12 thoracic vertebrae, implying that the thorax is the same as the upper trunk. In SNOMED CT, the thoracic vertebrae are not included in the thoracic cage; this is consistent with Foundational Model of Anatomy and Terminologia Anatomica and adheres to the narrow meaning of the thorax. The updated model avoids classifications of thoracic spine conditions /procedures under conditions/procedures of the body wall or thorax.

Changes in additional hierarchies: Disorders of thoracic spine have been excluded from the disorders of thorax.

2.3.3. Inactivation of 81861006 |Prosencephalon structure (body structure)|

The existing concept relating to the 'prosencephalon' has been inactivated with reason ambiguous as it possibly related to the adult cerebrum or the forebrain vesicle embryologically - the concepts have been structured and named using the Terminologia Anatomica 2 convention.

2.3.4. New Concepts - Third of Rectum

New concepts have been added for the lower, middle, and upper third of the rectum.

Number of concepts edited (approx): 6

2.3.5. New Concepts - Paraesophageal Lymph Nodes

New concepts for upper/middle/lower thoracic paraesophageal lymph nodes have been added to support the recording of malignant neoplasms. The esophageal lymph node has been moved to a subtype of lymph node of body region and the synonym Lymph node of AJCC Station 8 has been inactivated. A new concept Thoracic paraesophageal lymph node has been added for the AJCC Station 8.

Number of concepts edited (approx): 10

2.3.6. 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. Procedure

2.4.1. Inactivation of Descriptions - "RAST" and "RAST test'

Based on a proposal by the Allergies and Hypersensitivities Clinical Reference Group, descriptions containing “RAST” and “RAST test” have been inactivated from the concepts in the subhierarchy 104380004 |Allergen specific antibody measurement (procedure)| as they are not considered true synonyms.

Immunoassays for immunoglobulin specific to an allergen of interest are widely used in the diagnosis of allergic disease. These tests are often incorrectly referred to collectively as "radioallergosorbent tests" ("RAST") because they were the earliest immunoassays to be used extensively.

2.5. Pharmaceutical / biologic product (product)

2.5.1. Updates for Dose Form

Following discussion at the Drug Extension User Group (DEUSG) it was agreed that 'lyophilized' is out of scope for the International edition of SNOMED CT.

• 7 concepts for dose forms for lyophilized powder have been inactivated.
• 6 further concepts for dose forms were recommended for inactivation with 2 new replacement concepts being created. 

Further information is available here.

Number of concepts edited (approx): 15

Concept inactivations: 13

2.5.2. International Unit in Descriptions for Clinical Drugs

'International Unit' as a description is arbitrary and to be understood each product requires reference to a particular bioefficacy specification for that entity. Therefore, 'international' is not meaningful or comparable as a description at Clinical Drug level. International unit will be represented as 'unit' in Clinical Drug descriptions. 20 concepts have had descriptions changed to 'unit'  Note: abbreviations will not be used and accompanying editorial guidance has been created.

2.6. Physical Object

2.6.1.  Review 224899006 | Walking aid (physical object) | and 705403001 | Walking assistive device (physical object) and descendants

Content updates for this Content Tracker have been completed for the January 2024 release.

2.7. Collaboration/Harmonization Agreements

2.7.1. Social Care

73 concepts (24 Finding and 47 Procedure) have been promoted from the Australian, Norwegian, UK and US extensions to support the older people social care domain.

2.7.2. Convergent Medical Terminology (CMT)

Work is ongoing for this content area.

2.7.3. Orphanet

Working in collaboration with Orphanet (http://www.orpha.net/consor/cgi-bin/index.php), the additional content development required to expand the map for 2023 is complete.

Collaborative efforts are ongoing to update rare disease concepts in SNOMED CT to maintain alignment with Orphanet for 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.

2.7.4. 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 

2.7.5. International League Against Epilepsy (ILAE)

In line with approved harmonized terminology, this project is working on alignment including restructuring to update the hierarchy  << 313307000 |Epileptic seizure (finding)|.

Further information about the changes is available here. 

2.7.6. Gravity Project

Two procedure concepts relating to intimate partner violence services and six clinical finding concepts relating to being unable to obtain <x> due to limited financial resources have been added to support the Gravity project.

2.8. Internal Quality Improvement

2.8.1. Machine Readable Concept Model (MRCM) Changes

No  changes have been made for the January 2024 release.

Future changes that are currently in progress can be viewed via the MRCM Daily Build Browser

Please see early visibility for future planned changes to MRCM.

2.8.2. OWL Axiom Expressions for Annotation Properties

The new annotation properties should be represented in the OWL expression axiom refset as follows:

• The 1295447006 |Annotation attribute (attribute)| is correctly represented as subClassOf

  • 01300ccd-d1d7-417d-a70a-f688e72c4d8c 20231201 1 900000000000012004 733073007 1295447006 SubClassOf(:1295447006 :246061005)

• However, all subconcepts of 1295447006 |Annotation attribute (attribute)| should be represented as "SubAnnotationPropertyOf", instead of "subClassOf" as they currently are.

  • e6cd65fe-cb81-4db4-9ac4-040dc74fce28 20231201 1 900000000000012004 733073007 1295448001 SubClassOf(:1295448001 :1295447006)

  • 3729ce47-a96e-4dc7-9eff-83c34740c414 20231201 1 900000000000012004 733073007 1295449009 SubClassOf(:1295449009 :1295447006)

They should therefore be changed to:

• SubAnnotationPropertyOf(:1295448001 :1295447006)

• SubAnnotationPropertyOf(:1295449009 :1295447006)

However, the authoring tool will then need to be updated to ensure all new subconcepts of 1295447006 |Annotation attribute (attribute)| will be represented as SubAnnotationPropertyOf() in the future.  Numerous other tools will also need to be updated first in order to correctly consume the new format.

There are numerous systems that require updating, and that this will therefore need to be carefully tested and rolled out over the next few months.  As the potential impact was analysed and deemed to be low, the Annotations deployment will still go ahead as planned in the January 2024 International Edition release, whereas these axiom updates will be published in subsequent releases.  Please, therefore, be aware that this issue will persist for the first few International Edition releases of 2024.

2.9. SNOMED CT derived products

2.9.1. 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 Edition 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 |SNOMED CT to ICD-10 extended map (foundation metadata concept).

The ICD-10 Mapping Technical Guide (including exemplars) is hosted here https://confluence.ihtsdotools.org/display/DOCICD10

2.9.2. 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 January 2024

The map provided for the January 2024 International Edition has been updated, and now represents a complete map from SNOMED CT International Edition to ICD-10 2016 version.

• 275 newly authored concepts have been added and mapped.

• The SNOMED to ICD-O (morphology) map has 5 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

2.9.3. 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

The RF2 package convention dictates that all relevant files are included, regardless of whether or not there is content to be included in each release.  Therefore, the package contains a mixture of files which contain both header rows and content data, and files that (intentionally) include only header records.  The reason that these "empty" files are included in the package is to draw a clear distinction between:

1. ...files that have been deprecated (and therefore removed from the package completely), due to the content no longer being relevant to RF2 in future releases 

2. ...files that happen to contain no data in this particular release (and are therefore included in the package with just a header record), but are still relevant to RF2, and could therefore contain content in future releases.

This allows users to easily distinguish between the two scenarios, as otherwise if files in option 2 were left out of the package it could be interpreted as an error, rather than an intentional lack of content in that release.

3.3.2. Configuration file in the RF2 package, containing Release Metadata 

A configuration file ("release_package_information.json") is now included in the International Edition, containing metadata about the Release package itself, including:

• effectiveTime
  

• previouslyPublishedPackage

• languageRefset(s)

• licenceStatement

The metadata will be continually refined going forward, so if you have any ideas about useful information to include please send them to release@snomed.org, along with a business case explaining how the information would benefit stakeholders.  Please be aware that use cases will then be assessed by SNOMED International, and new metadata will only be added for strong business cases.  

3.3.3. Changes to the Identifier file format

In line with the proposals documented here:  https://confluence.ihtsdotools.org/mag/snomed-international-proposal-to-change-the-rf2-identifier-file-specification - the International Edition Release includes the following changes to the format of the Identifier files:

• < identifierSchemeId    alternateIdentifier    effectiveTime    active    moduleId    referencedComponentId           ...to
• > alternateIdentifier    effectiveTime    active    moduleId    identifierSchemeId    referencedComponentId

These improvements were introduced in the September 2023 International Edition release, and will be used in all future International Edition releases until further notice.

3.3.4. Changes to the International Edition package format

In line with the new implementation of Annotations, two new refsets have been added to the International Edition Release package, from December 2023 onwards:

• der2_scsRefset_ComponentAnnotationStringValueSnapshot_INT_20240101.txt
• der2_sscsRefset_MemberAnnotationStringValueSnapshot_INT_20240101.txt

These refset files are empty for the January 2024 release, whilst content is authored in future editing cycles.  However, they will then be populated with Annotations data from one of the future 2024 International Edition releases onwards (date to be confirmed).  These improvements were introduced in the December 2023 International Edition release, and will be used in all future International Edition releases until further notice.

If you have any feedback on the format of these new files please provide it URGENTLY, as changes can potentially be made now (subject to relevant approvals), before the files are populated. 

3.3.5. Proposed change to the Annotations Refset format

3.3.6. Early visibility of impending changes in the upcoming 2024 Monthly International Edition releases

Please see the early visibility Confluence page for details of forthcoming changes.