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 October 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 October 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 October 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 October 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. Review of CRS Requests in “Awaiting agreement compliance” Status from SNOMED CT – LOINC Cooperation Project

CRS requests that were in “Awaiting agreement compliance” status due to the previous cooperative agreement between SNOMED International and Regenstrief Institute, Inc. have been reviewed in light of the new cooperative agreement, the latest SNOMED CT Editorial Guide, and the latest CRS guidance documents. Concepts deemed in scope have been added. This review has now been completed.

2.3. 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 October 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. 

2.3.1.  Remodel of Obstetric Procedures

Work has been undertaken to resolve the suboptimal concept model and classification for over 100 concepts that are related to procedures on gravid uterus.  The scope for this work was:

<< 71388002 |Procedure (procedure)| : << 363704007 |Procedure site (attribute)| = << 9258009 |Gravid uterus structure (body structure)|

Remodeling of obstetric procedures has been achieved by assigning two GCI axioms to "Obstetric procedure" and introducing the "occurrence" attribute for modeling detailed maternal perinatal period and pregnancy time period for its subconcepts. These updates have improved modeling consistency and addressed incomplete classification results. The total number of obstetric procedures has increased from 380 to over 560.

2.3.2. Add concepts: <procedure> during <event>

Work has been completed for content tracker IHTSDO-102 with associated new editorial guidance for 'Procedure during period of life'.

2.3.3.  Update for  T-cell Lymphoblastic Leukemia/Lymphoma concepts

Expert pathology review of T-cell lymphoblastic leukemia/lymphoma concepts has been undertaken. 

2.4. Body Structure 

2.4.1. Update for Anterior and Posterior Rami of Spinal Nerves

Concepts relating to anterior and posterior rami of the spinal nerves have been updated. Classification derived content relating to the four upper ventral (anterior) rami has been inactivated.

2.4.2.  Update for Occipital Bone Structures

Occipital bone structures have been reorganized by the basilar, lateral and squamous regional parts.

2.4.3. Update for Choroid

Structures of the choroid have been rearranged into three regions and four layers. Changes were made to 35 concepts including the addition of new concepts and inactivation of ambiguous concepts.

2.4.4. Remodel for Acetabular Cartilage Complex

Acetabular cartilage complex and its relationships to articular cartilage, growth plate, and bone have been updated.

2.4.5. Inactivation of Left Eye/Right Eye

The anatomy concepts 8966001 |Left eye structure (body structure)| and 18944008 |Right eye structure (body structure)| have been inactivated with reason ambiguous and by eye region/proper. These inactivated concepts are subconcepts of eye proper. The replacements by the new eye proper concepts has no impact on classification results.

2.4.6. Update for Joints and Subregions of Foot

Resolved missing and incorrect relationships between the joints and the subregions of the foot, hindfoot, midfoot, and forefoot.

New concepts have been added for "Cuneocuboid joint" and "Subtalar joint complex". The complex subsumes "Subtalar joint" and "Talocalcaneonavicular joint".

2.4.7. 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.

2.5. Clinical Finding

2.5.1. Inactivation of 308971001 |Payment for service status (finding)| and Descendants

This area of content originated from NHS Read codes and due to it's jurisdiction-specific and administrative nature falls outside the scope of the international edition as not related to direct clinical care or management of care. 70 concepts have been inactivated without replacement following member request and consultation with the community of practice. For further information please see the briefing note.

2.5.2. Update for Synovial Cyst

Synovial popliteal cyst is the most common cyst of knee. However, there are other cysts of knee. New concepts for synovial popliteal cyst have been created and inappropriate synonyms have been inactivated from cyst of knee.

2.5.3.  Inactivation of 'Attends/Attending X'

Around 40 concepts with FSN "Attends X" or "Attending X" in the clinical finding hierarchy e.g., 160766005 |Midwife attends 14-16 days post-discharge (finding)|, have been inactivated as they are administrative concepts.

2.6. Procedure

2.6.1. Update for 129348007 |Z-plasty - action (qualifier value)|

129348007 |Z-plasty - action (qualifier value)| has been updated with a new FSN of 129348007 |Local flap reconstruction by Z-plasty - action (qualifier value)| and a new parent of 1193841002 |Local flap reconstruction - action (qualifier value)|.

13 procedure concepts referring to Z-plasty have been remodeled to match the template model for flap procedures. One concept 177414001 |Z plasty to head or neck (procedure)| has been inactivated and replaced with 2 separate concepts.

2.7. Situation with Explicit Context

2.7.1. Update Hierarchy 271903000|History of pregnancy (situation)|

The hierarchy 271903000|History of pregnancy (situation)| has been remodeled with description changes, concept inactivation, update to model, addition of subtypes to the hierarchy. Approximately 80 concepts have been updated.

The following concepts have been inactivated:

• 161811009|History of perinatal fetal loss (situation)|
• 726626004|History of neonatal death (situation)|

Replacement concepts have been added:

• 1290167007 |Past pregnancy history of neonatal death (situation)|
• 1290171005 |Past pregnancy history of late neonatal death (situation)|
• 1290170006 |Past pregnancy history of early neonatal death (situation)|
• 1290143004 |Past pregnancy history of perinatal death (situation)|
• 1290142009 |Family history of perinatal death (situation)|
• 1290168002 |Family history of neonatal death (situation)|

The FSN and preferred term for content in this hierarchy has been updated to explicitly specify "Past pregnancy history of" and the editorial guidance has been updated to align with these changes. Pregnancy related concepts in situation hierarchy have been remodeled to subsume under 271903000|History of pregnancy (situation)|.

2.7.2. Inactivation of Content 'X-Result Not Back'

Four concepts of the type "X result not back (situation)," e.g., 168709001 |Soft tissue X-ray result not back (situation)|, have been inactivated as they are out of scope for the international edition.

2.8. Social Context

2.8.1. Inactivation of Subtypes of 125676002|Person (person)|

Two concepts in the person hierarchy have been inactivated. The Editorial Guide states that the Subject relationship context (attribute) is used to specify the subject of the Clinical finding or Procedure being recorded, in relation to the subject of the record; therefore, these two concepts are unnecessary:

• 444145006 |Partner in relationship with subject (person)| - historical association to 262043009 |Partner in relationship (person)|
• 444210007 |Cohabitee in relationship with subject (person)| - historical association to 394921008 |Cohabitee (person)|

2.9. Collaboration/Harmonization Agreements

2.9.1. Convergent Medical Terminology (CMT)

357 new concepts have been added for the October 2023 release. Content inclusions were predominately musculoskeletal disorders but also included injuries, neoplastic disorders and neoplastic history concepts.

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. 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 

2.9.4. 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. 

2.9.5. Gravity Project

Work is ongoing for this content area.

2.10. Internal Quality Improvement

2.10.1. Machine Readable Concept Model (MRCM) Changes

The following changes has been made to the MRCM for the October 2023 International Edition:

• The MRCM for Administration of substance via specific route (procedure) is no longer needed. The domain 433590000 |Administration of substance via specific route (procedure)| is replaced by a new concept 1285465008 |Administration via specific route (procedure)|. Instances of “Administration of substance via X specific route (procedure)” have been replaced with concepts of type “Administration via X specific route (procedure)”. This change is part of the Substance-Drug project and allows for the unambiguous subsumption of the subtypes, if and once instances of 363701004 |Direct substance (attribute)|are modeled with subtypes of 373873005 |Pharmaceutical / biologic product (product)|. 

• Extend the domain of 246454002 |Occurrence (attribute)| by including << 71388002 |Procedure (procedure)|. The following is the expected MRCM range after the change:
  • 246454002 |Occurrence (attribute)| << 272379006 |Event (event)| OR << 404684003 |Clinical finding (finding)| OR << 71388002 |Procedure (procedure)|

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.

2.11. 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 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 |ICD-10 complex map reference set (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 October 2023

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

• 472 newly authored concepts have been added and mapped.

• The SNOMED to ICD-O (morphology) map has 7 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

2.11.2. 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