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 February 2023 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 February 2023 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 February 2023 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 February 2023 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 February 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.  Update Model for 253273004 |Cardiac septal defects (disorder) and Descendants

253273004 |Cardiac septal defects (disorder)| and descendants has been remodeled to inactivate the associated morphology 6920004 |Defect (morphologic abnormality)| and remodel the concepts with an appropriate replacement.

6920004 |Defect (morphologic abnormality)is scheduled for inactivation please see the briefing note for further information.

2.2.2. Update Concepts Using Description 'Fetal and/or neonatal'

A number of classification derived concepts using the pattern 'fetal and/or neonatal' in descriptions have been reviewed and inactivated or updated. 

2.2.3. Inactivation of 'Open wound with tendon involvement' Concepts

Classification derived concepts of the form "Open wound with tendon involvement" have been inactivated with replacement by "Open wound" and "Laceration of tendon" concepts.

2.2.4. Inactivation of 'X by body site' Concepts in Various Hierarchies

Concepts that include "X by body site" in multiple hierarchies have been inactivated, e.g., 371571005 |Imaging by body site (procedure)| and 301810000 |Infection by site (disorder) because these are classification groupers with no clinical use.

2.3. Body Structure 

2.3.1. New Lateralized Anatomy Concepts

New lateralized concepts have been added to the body structure hierarchy in the areas of: skin of cheek, buccal mucosa, upper region of buccal mucosa and lower region of buccal mucosa. 

New concepts have also been added to represent right, left and middle third of upper and lower lip.

2.3.2. Revision of 306720004|Synovial structure (body structure)| and Descendants

A review of 306720004|Synovial structure (body structure)| and subtypes has been undertaken to align the content in this area with the new model detailed here.

Concepts in the clinical finding, procedure, specimen, situation with explicit context, hierarchies have also been updated to align with the changes to anatomy. 

2.3.3. Revision of 410783001 |Structure of tendon sheath within upper limb (body structure)|

410783001 |Structure of tendon sheath within upper limb (body structure)| and descendants have been reviewed to update the model and descriptions for about 60 concepts. This has improved the clarity of a tendon sheath running through multiple adjacent regions and segments of a tendon sheath within a region.

410787000 |Structure of flexor digitorum tendon sheath (body structure)| has been inactivated with reason ambiguous and association targets possibly equivalent to 1216997004 |Structure of flexor tendon sheath within digit of hand (body structure) and 56334007 |Structure of common tendon sheath of flexor muscle within forearm and/or wrist and/or hand (body structure)|.

43558007 |Structure of retinaculum flexorum of hand (body structure)| has been remodeled to reflect that it forms the roof of the carpal canal.

24367005 |Structure of flexor pollicis longus muscle tendon sheath (body structure)| is a tendon sheath within the forearm, wrist, and hand, and a new concept of its regional part within the thumb has been added.

Descriptions have been updated to improve clarity for segments of tendon sheath within regions.

2.3.4. New Concept 1264351007 |Structure of distal thoracic aorta and/or proximal abdominal aorta (body structure)|

A new concept 1264351007 |Structure of distal thoracic aorta and/or proximal abdominal aorta (body structure)| has been added. It represents a continuous region that includes parts from both the thoracic and abdominal aorta.

The model for content in the disorder and procedure hierarchies relating to the thoracoabdominal aorta (approximately 15 concepts) has been updated to include the new body structure.

2.3.5. Description Update for Blood Vessels of Upper Extremity

The descriptions for blood vessels of the upper extremity (about 50 concepts) have been updated to align with editorial guidance.

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. Clinical Finding

2.4.1. Update for 'At Risk' Concepts

Content of the pattern "At risk of x' have been updated with a new model that allows many of the concepts to be sufficiently defined. This has resulted in an improved hierarchy and elimination of some duplicates in this previously primitive hierarchy of clinical findings.

2.4.2. Update 205473008|Mesomelic dysplasia (disorder)| and Descendants

205473008|Mesomelic dysplasia (disorder)| previously grouped subtype concepts which included both rhizomelia and mesomelia.  

A new concept 1263463009 |Rhizomelic dysplasia (disorder) has been added as a sibling of 205473008 |Mesomelic dysplasia (disorder)|

Text definitions have been added and content that was previously a descendant of 205473008|Mesomelic dysplasia (disorder)| has been reviewed and in some cases remodeled under the correct supertype.

237836003|Short stature disorder (disorder)| has been inactivated as parent of 205473008|Mesomelic dysplasia (disorder)| as this relationship is not true in all cases.

2.4.3. Update Hierarchy 111246005 |Arthrogryposis (disorder)|

The inactive concept 205402004 |Arthrogryposis multiplex congenita (disorder)| has been reactivated in response to feedback from an expert group. Stated subtypes have been added. 

77016009 |Amyoplasia congenita disruptive sequence (disorder)| has been inactivated and replaced by 1264194006 |Congenital amyoplasia (disorder)| as part of the work being undertaken for this content area.

2.4.4. Inactivation of 118222006 |General finding of observation of patient (finding)|

118222006 |General finding of observation of patient (finding)| has been inactivated with a historical association target of 404684003|Clinical finding (finding)|.  

The descendant count for this concept was 4237 and these previous subtype concepts have been reassigned.

2.5. Procedure

2.5.1. Inactivation of 9924007|Excision and replacement (procedure)|

The intermediate primitive concept 9924007 |Excision and replacement (procedure)| has been inactivated.

Approximately 30 concepts relating to grafting of blood vessel have had an update to the model as part of the work undertaken to inactivate this concept.

2.5.2. Revision of 74415009|Repair of aneurysm with graft of artery (procedure)| and Descendants

The model for 74415009|Repair of aneurysm with graft of artery (procedure)| and subtypes has been updated to resolve issues with multiple role groups for approximately 30 concepts.

2.6. Qualifier Value

2.6.1. Update for 307159006 Pregnancy time period (qualifier value) and Descendants

307159006 Pregnancy time period (qualifier value) and descendants have been reviewed and a small number of concepts have been added to make coverage of this area of content more comprehensive.

For example, a new qualifier value explicitly covering 1260236009 |Maternal antenatal and/or intrapartum and/or postpartum period (qualifier value)| has been added.

Definitions have been added to aid modeling and interpretation.

For example: ‘pregnancy period’ covers the time from conception until the end of the third stage of labor; and the value of ‘postpartum' has been defined as including the time period up to 6 weeks, in contrast to ‘postnatal’ which has been defined as stretching up to 52 weeks after delivery.

2.7. Substance

2.7.1. Update for 303517000 |Arteriovenous graft material (substance)|

Subsumption between 303517000 |Arteriovenous graft material (substance)| and 260667007 |Graft (substance)| has been updated to improve the classifications of 25 concepts in the procedure hierarchy.

2.8. Collaboration/Harmonization Agreements

2.8.1. Convergent Medical Terminology (CMT)

75 new CMT concepts with a focus on the injury domain have been added.

2.8.2. 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.

2.8.3. 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. 

2.9. Internal Quality Improvement

2.9.1. Machine Readable Concept Model (MRCM) Changes

The following changes have been made for the February 2023 release:

• Extend the range of 719722006 |Has realization (attribute)| by including 71388002 << |Procedure (procedure)|, << 272379006 |Event (event)|, << 404684003 |Clinical finding (finding)|.

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

Please see early visibility for future 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 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)|.

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 February 2023

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

• 543 newly authored concepts have been added and mapped.

• The SNOMED to ICD-O (morphology) map has 2 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

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 early visibility for details of forthcoming changes.