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 May 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 May 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 May 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 May 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 May 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. Inactivation of 6920004|Defect (morphologic abnormality)|

As part of the Quality Initiative, 6920004 |Defect (morphologic abnormality)| has been inactivated with reason ambiguous.

More information about this inactivation can be found in this briefing note.

2.2.2. Inactivation of 40024006|Retinal defect (disorder)|

40024006 |Retinal defect (disorder)| has been inactivated with reason ambiguous. Subtype concepts have been remodeled and where appropriate, inactivated and replaced.

2.3. Body Structure 

2.3.1.  New Subtypes of 84782009|Peripheral nerve structure (body structure)|

New concepts for peripheral nerve structures have been added. Three duplicate concepts in this area of content have been inactivated.  

2.3.2. 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. Qualifier Value

2.4.1. Inactivation of Descendants of 129284003|Surgical action (qualifier value)|

45 concepts that are descendants of 129284003 |Surgical action (qualifier value)| have been inactivated.

Reason for inactivation:

• 35 concepts with no usage or descendants
• 4 concepts with 3 or less descendants
• 5 concepts with less than 2 descendants and low usage

A complete list of the concepts inactivated is available here.

2.5.  Clinical Finding

2.5.1. Epilepsy

Content changes have been made in the following areas in collaboration with the International League Against Epilepsy (ILAE):

• Seizures with a focus on structural and semiological focal seizures
• Epilepsy with focus on generalized epilepsies

These changes include 40 new concepts and 64 concept inactivations as well as changes to descriptions and additions of text definition.

Further information can be found here and also in Section 2.7 (Collaboration/Harmonization Agreements) of these release notes.

2.5.2. Inactivation of Measurement Finding Concepts

The following measurement findings concepts have been inactivated as they do not comply with editorial guidance:

• Blood glucose finding concepts with the numeric value or range precoordinated, e.g., 166915000 |Blood glucose 1.5-2.4 mmol/L (finding)| - 7 concepts.

• Urine pH finding concepts with the numeric value precoordinated, e.g., 167309000 |Urine pH = 6.5 (finding)| - 7 concepts.

• 107651007 |Quantity finding (finding)| and 13 subtype concepts.

• "X in sample" finding concepts, e.g., 275791007 |Urea in sample (finding)| - 9 concepts.

2.6. Procedure

2.6.1. Inactivation of Procedure Concepts Containing "Substance"

Grouper concepts in the procedure hierarchy which contained the general term “substance” in their descriptions have been reviewed and inactivated where applicable.  

Specifically the groupers that were classification derived and/or had only one subtype.

This change will allow for the correct subsumption of the subtypes if and once the attribute values are subtypes of 373873005 |Pharmaceutical / biologic product (product)|.

2.7. Collaboration/Harmonization Agreements

2.7.1. Convergent Medical Terminology (CMT)

Content addition for this agreement is ongoing.

2.7.2. 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.

2.7.3. 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 

2.7.4. 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. 

2.7.5. Gravity Project

4 new concepts relating to education have been added for the May 2023 release to support the Gravity project.

2.8. Internal Quality Improvement

2.8.1. Machine Readable Concept Model (MRCM) Changes

There have been no changes for the May 2023 release.

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

Please see early visibility for future changes to MRCM.

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 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 May 2023

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

• 150 newly authored concepts have been added and mapped.

• The SNOMED to ICD-O (morphology) map has 3 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

2.9.2. 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 the early visibility page below for details of forthcoming changes:

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

3.3.2.1. Proposal to move the International Monthly release date to the first of each month

After initial consultation with the community, SNOMED International are proposing to change the dates of the International Edition from the end of each month, to the first of each month.  This would mean that in addition to all of the other months, the “January” release would move from 31st January to the 1st January, and the “July” release would move from 31st July to 1st July each year.  Further details of this proposal can be found in the Q&A blog post below, however if you have any concerns please provide feedback to release@snomed.org as soon as possible. 

• https://www.snomed.org/news/the-snomed-ct-international-edition-to-be-published-on-first-day-of-each-month