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 November 2023 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 November 2023 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 November 2023 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 November 2023 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 November 2023. 

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.  Remodel of Heart Valve Replacement Procedure Concepts

Work has been undertaken to resolve the suboptimal model and classification for heart valve replacement content:

• Heart valve replacement concepts have been remodeled as surgical replacement with distinction made between replacement of native valves and implanted prosthetic valves. Prosthetic valves include both mechanical and biological valves. For example, a heart valve replacement refers to surgical repair of native tissue using a prosthetic device whereas the replacement of an implanted valve replaces a direct device.
• For the procedures related to the atrioventricular valve, these procedures refer to the developmental structure “Atrioventricular (non-mitral, non-tricuspid) valve structure/ (body structure)”. The mitral and tricuspid valves refer to the mature structures collectively known as the atrioventricular valves and they are distinct from the AV non-mitral, non-tricuspid valve.
• Surgical REMOVAL and REPLACEMENT may not occur at the same point in time so a surgical replacement procedure may not subsume under surgical REMOVAL. These surgical methods are at the same level within the hierarchy.

2.2.2. Update for Concepts Using 'Caused by'

Concepts referring to 'Poisoning caused by (due to) organism sting or bite' have been updated for the November 2023 release. 

2.2.3. Remodel 1288025000 |Prosthetic arthroplasty of joint (procedure)|

The content in the subhierarchy 1288025000 |Prosthetic arthroplasty of joint (procedure)| and its 138 descendants have been reviewed as part of the ongoing quality improvement efforts.

These concepts were initially modeled using the METHOD = 425362007 |Surgical insertion - action (qualifier value)|. However, a more accurate representation was achieved by modeling them with 129338005 |Surgical implantation - action (qualifier value)| to better reflect the implantation of the prosthesis, making these concepts descendants of 782902008 |Implantation procedure (procedure)|.

The duplication was also resolved with 61557004 |Implantation of joint prosthesis (procedure)| inactivated as a duplicate of 1288025000 |Prosthetic arthroplasty of joint (procedure)|. As a result of these refinements, the hierarchy 1288025000 |Prosthetic arthroplasty of joint (procedure)| now includes 188 descendants, an increase from the original 138.

2.3.  Body Structure 

2.3.1. Remodel Subtypes of 245643006 |Structure of tooth surface (body structure)|

Subtypes of 245643006 |Structure of tooth surface (body structure)| which relate to multiple surfaces have been remodeled to include the top-level single surface concepts as parents.

For example:

• 245655000 |Structure of buccal occlusal tooth surfaces (body structure)| has gained the parents
  • 62579006 |Structure of vestibular surface of tooth (body structure)| and
  • 83473006 |Structure of occlusal surface of tooth (body structure)|

2.3.2. New Content 1290361000 |Structure of vitreoretinal interface (body structure)|

The following new concepts have been added along with lateralized and entire subtypes:

• 1290361000 |Structure of vitreoretinal interface (body structure)| 
• 1290373000 |Structure of posterior cortex of vitreous body (body structure)|
• 1290373000 |Structure of posterior cortex of vitreous body (body structure)|

2.3.3. New Content 1290966004 |Structure of deep pelvic vein (body structure)|

Concepts included within the class of deep pelvic vein have been augmented. Two additional interosseous vein concepts have been added relating to tributaries of the ulnar vein of lower leg.

2.3.4. Update Model for 244411005 |Iliac vein structure (body structure)|

244411005 |Iliac vein structure (body structure)| has been remodeled to include an IS_A relationship to new concept 1290966004 |Structure of deep pelvic vein (body structure)|.

The previous IS_A relationship from 244411005 |Iliac vein structure (body structure)| to 119556008 |Structure of deep vein of lower limb (body structure)| has been inactivated.

2.3.5. 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. Update Hierarchy 263026000|Dislocation of perilunate joint (disorder)|

A new supertype concept has been added 1290805004 |Dislocation of joint of lunate (disorder)| with subtypes:

• 1290885002 |Dislocation of lunate bone (disorder)|
• 263026000 |Dislocation of perilunate joint (disorder)|

Subtype concepts have been updated to align with the new model.  A text definition has been added for 263026000 |Dislocation of perilunate joint (disorder)|.

The fully specified name has been updated for 264132003 |Structure of joint of lunate (body structure)|.

2.4.2. Update 128609009 |Intracranial aneurysm (disorder)| and 233983001 |Ruptured cerebral aneurysm (disorder)|

The finding sites for 128609009 |Intracranial aneurysm (disorder)| and 233983001 |Ruptured cerebral aneurysm (disorder)| have been updated to 281138005 |Intracranial vascular structure (body structure)|.

New concepts have been added:

• 1293173007 |Aneurysm of intracranial artery (disorder)|
• 1293174001 |Aneurysm of intracranial vein (disorder)|

'Cerebral aneurysm' is restored as a synonym for 128609009 |Intracranial aneurysm (disorder)|.

2.4.3. Update 735541006 |Dissociative neurological symptom disorder (disorder)|

After consultation with the Mental and Behavioural Health Clinical Reference Group, it was confirmed that dissociative neurological symptom disorder/functional neurological disorder and conversion disorder are synonymous. Content in this area has been updated to remove duplication and improve the structure of the sub-hierarchy 735541006 |Dissociative neurological symptom disorder (disorder)|. While this hierarchy formerly consisted of 12 descendants, it has now expanded to 31.

The update has resolved this content tracker.

2.4.4. Update Subtypes of 235853006 |Angiodysplasia of intestine (disorder)|

Angiodysplasia, vascular ectasia and angiectasia are considered synonymous, however angiodysplasia is the preferred term when discussing angiectasia in the gastrointestinal tract. New content has been added and descriptions have been updated for this content area.

The concept 71072006 |Angiodysplasia (morphologic abnormality)| has been inactivated.

2.5. Procedure

2.5.1. Inactivation of Subtypes of Injection for Local Action

Approximately 25 concepts with the format of 'Injection of X for local action' have been inactivated with reason 'classification-derived component'.

The historical association target is the injection procedure relevant to each concept without the 'local action'.

2.6. Substance

2.6.1. Review of 35331000 |Toxic substance (substance)|

35331000 |Toxic substance is an ambiguous concept and has been inactivated; it can refer to any substance that has been used in an amount that is harmful for health (including medication), a toxin, heavy metals, or preservatives - not all of these are currently children of 35331000 |Toxic substance (substance)|.

In addition, concepts defined by 35331000 |Toxic substance (substance)| have been reviewed;  their descriptions and model have been updated where applicable, specifically where the FSN and attribute/value do not match.

2.7. Foundation Metadata Concept

2.7.1. Annotation Reference Set

Four new concepts have been added for the forthcoming annotation reference sets:

• 1292994003 |Component annotation with component value reference set (foundation metadata concept)|
• 1292992004 |Component annotation with string value reference set (foundation metadata concept)|
• 1292996001 |Member annotation with component value reference set (foundation metadata concept)|
• 1292995002 |Member annotation with string value reference set (foundation metadata concept)|

2.8. Collaboration/Harmonization Agreements

2.8.1. Convergent Medical Terminology (CMT)

Work is ongoing for this content area.

2.8.2. 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.

2.8.3. 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 

2.8.4. 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. 

2.8.5. Gravity Project

Work is ongoing for this content area.

2.9. Internal Quality Improvement

2.9.1. Machine Readable Concept Model (MRCM) Changes

There are no changes to the MRCM for the November 2023 International Edition:

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.

2.10. SNOMED CT derived products

2.10.1. 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

2.10.2. 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 November 2023

The map provided for the November 2023 International Edition has been updated, and now represents a complete map from SNOMED CT International Edition to ICD-10 2016 version.

• 210 newly authored concepts have been added and mapped.

• The SNOMED to ICD-O (morphology) map has 39 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

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

Please see the early visibility page below for details of forthcoming changes:

• https://confluence.ihtsdotools.org/display/RMT/2023+Early+Visibility+Release+Notifications