Introduction

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. The SNOMED CT US NL Edition is a combination of the full June 2022 SNOMED CT International Edition and the US NL Extension of SNOMED CT.

The International Health Terminology Standards Development Organisation (IHTSDO^®), trading as 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. The SNOMED CT US NL Edition is developed and maintained by the United States National Library of Medicine NL NRC and is available to authorized Unified Medical Language System (UMLS) Metathesaurus Licensees. This material includes SNOMED CT which is used by permission of the IHTSDO. All rights reserved.

SNOMED CT was originally created by the College of American Pathologists. "SNOMED" and "SNOMED CT" are registered trademarks of IHTSDO. You must have a UMLS Metathesaurus license to access SNOMED CT US Edition data files. License information is available from NLM (https://www.nlm.nih.gov/healthit/snomedct/snomed_licensing.html).  

1.1 Background

Background

This document provides a summarized description of the content changes included in the This document provides a summarized description of the content changes included in the September 2022 release of the SNOMED Clinical Terms® US Terms® NL Edition.

It also includes technical notes detailing the known issues which have been identified. These are content or technical issues where the root cause is understood, and the fix has been discussed and agreed, but has yet to be implemented.

This document is available as a web resource as well as alongside the September 2022 US Edition release (https://www.nlm.nih.gov/healthit/snomedct/us_edition.html). 

NL Edition release. 

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. These Release Notes should be used in combination with the SNOMED CT June July 2022 International Edition - SNOMED International Release notes. 

2 Content Development Activity 

2.1 Summary

The September 2022 SNOMED CT US Edition marks the tenth release with content authoring tooling and release production provided by SNOMED International Managed Service. Quality assurance of the release was completed by both NLM and SNOMED International. Additionally, in October 2017, NLM sunset the United States SNOMED CT Content Request System and migrated to the SNOMED International hosted and maintained US CRS (https://us-request.ihtsdotools.org). 

2.1.1 September 2022 US Edition of SNOMED CT Statistics 

 Changes to the release format

Since the last release, our SNOMED NRC has changed to a new authoring platform. This has necessitated a number of changes in our release. These changes are described in sections 3.3 & 3.4. Please read these sections carefully, as they may require you to change your import script.

 National Terminology Server

The National Terminology Server provides an easy method of accessing the latest SNOMED edition in the FHIR R4 format. Using this server is free of charge. More information can be found at https://www.nictiz.nl/standaardisatie/terminologiecentrum/nationale-terminologieserver/ and https://github.com/terminologieserver.

Content Development Activity 

Summary

The September 2022 SNOMED CT NL Edition contains content authoring tooling and release production provided by SNOMED International Managed Service. Quality assurance of the release was completed by both the NL NRC and SNOMED International. 

September 2022 NL Edition of SNOMED CT Statistics 

These statistics include the content from the June 2022 International Edition and the September 2022 US NL Edition.

These statistics These statistics include the content from the September 2022 US Extension NL Edition.

2.2.1 SNOMED CT to ICD-10-CM map 

The purpose of the SNOMED CT to ICD-10-CM map is to support semi-automated generation of ICD-10-CM codes from clinical data encoded in SNOMED CT for reimbursement and statistical purposes. All current pre-coordinated SNOMED CT concepts from the US Edition (US Extension + International release) within three hierarchies, (Clinical findings, Events, and Situations with Explicit Context) are potentially in scope for mapping to ICD-10-CM. 

The SNOMED CT to ICD-10-CM map is released in RF2 format within the US Edition, as well as a standalone download (https://www.nlm.nih.gov/research/umls/mapping_projects/snomedct_to_icd10cm.html). The map is also available in a human readable format (tls_Icd10cmHumanReadableMap_US1000124_YYYYMMDD.tsv) contained within a standalone download - SNOMED_CT_to_ICD-10-CM_Resources_YYYYMMDD.zip.

The SNOMED CT to ICD-10-CM map is released as Refset 6011000124106 | ICD-10-CM extended map reference set (foundation metadata concept)|. The map data are in the file xder2_iisssccRefset_ExtendedMapSnapshot_US1000124_YYYYMMDD.txt, which is in the Map folder under Refset in the Snapshot Release Type folder.  

PLEASE NOTE: Starting with the 2019 September SNOMED CT US Edition (20190301) release, the SNOMED CT to ICD-10-CM map refset data will be maintained as per the SNOMED CT RF2 specifications. 

Additional map refset information can be found in the SNOMED CT to ICD-10-CM Release Notes (doc_Icd10cmMapReleaseNotes_Current-en-US_US1000124_YYYYMMDD.pdf) found in the standalone download or online. Technical information (doc_Icd10cmMapTechnicalSpecifications_Current-en-US_US1000124_YYYYMMDD.pdf) for the map can also be found in the standalone download. 

On September 26, 2019, an updated version of the map (6011000124106 | ICD-10-CM complex map reference set (foundation metadata concept)| ) was released. This updated version included an appending of the previously released mapping refset data, originally pulled from the 20190301 release. The newly released version, which includes all of the previously released data, now includes 260,749 mapped records. This is now considered the baseline for the SNOMED CT to ICD-10-CM map. 

2.2.2 Route of administration

The NLM maintained Route of administration reference set (442311000124105 | Route of administration reference set) is located in the file der2_Refset_Simple(Snapshot, Delta, Full)_US1000124_YYYYMMDD.txt, which is in the Content folder under Refset, in each of the three RF2 Release Type folders. The refset contains a set of terms related to the location of administration for clinical therapeutics. The purpose of the Route of Administration refset is to define a portion of which can be used in the Drug Listing section of Structured Product Labeling (SPL), or for documentation and encoding of clinical information regarding substance administrations. Only concepts that are subtypes of the concept 284009009 | Route of administration value (qualifier value) are included in the refset. Please note the 442311000124105 | Route of administration reference set has been in static status since 2014 September US Edition release (20140901). 

The Route of Administration concepts are now maintained as a value set on the NLM Value Set Authority Center (VSAC) (https://vsac.nlm.nih.gov/valueset/2.16.840.1.113762.1.4.1018.98/expansion). Users are required to have a UMLS account to access VSAC. If you don't have a UMLS account, you can request one here: https://uts.nlm.nih.gov/uts/signup-login

2.2.3 Transitive closure file

NLM provides a transitive closure script and generated transitive closure table within the SNOMED CT US Edition release. The transitive closure is the complete set of relationships between every concept and each of its super-type concepts (parents and ancestors). The transitive closure files can be used to support SQL queries when created and stored as a table in a relational database. If applied in a full release, it will contain the full history and allow for subsumption queries to be applied based on any release. The NLM transitive closure script provides a comprehensive view of all of the supertype ancestors of a concept derived by traversing all the 116680003 | is a | relationships between that concept and the root concept. The transitive closure table represents the transitive closure of the 116680003 | is a | relationships of all active concepts. NLM provides the transitive closure table in the US Edition release to provide support for easier implementation and a reference against which to check alternative algorithms. 

As of the September 2020 release, the Transitive Closure script, tls2_TranstiveClosure_US1000124_YYYYMMDD.pl, and the Transitive Closure table res2_TransitiveClosure_US1000124_YYYYMMDD.txt, are located in a separate bundled zip file (SnomedCT_TransitiveClosureResourcesRF2_PRODUCTION_YYYYMMDDT120000Z.zip) on the NLM US Edition page. For the table, the superTypeId is the id of the concept playing the supertype role, set to an Identifier of a concept. The subTypeId - Id of the concept playing the subtype role. Set to an Identifier of a concept. 

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 capacity within the current editing cycle, 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.

SNOMED CT derived products 

New reference sets

Changed reference sets

Technical Notes

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 capacity within the current editing cycle, 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.

In addition to the Known Issues reported by the IHTSDO for SNOMED CT International Edition (SNOMED CT June 2022 International Edition - SNOMED International Release notes), the following are Known Issues for the SNOMED CT NL Edition that have been identified and will be resolved in the next editing and production cycle: 

Resolved Issues

Resolved issues are Known Issues which were not fixed as part of the previous release lifecycle, but which have now been resolved for this September 2022 NL Edition. These can be issues found during the Pre-Production or Production phases of the testing of the current release, which were resolved before the final deployment of the final production release. Finally these can be issues which were reported or found during the testing phase, but which have been closed without any action taken. 

In addition to the Resolved In addition to the Known Issues reported by the IHTSDO for SNOMED CT International Edition (SNOMED CT June 2022 International Edition - SNOMED International Release notes), the following are Known Resolved Issues for the SNOMED CT US Edition that have been identified and will be resolved in the next editing and production cycle: September 2022 NL Edition:

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 for this September 2022 US Edition. These can be issues found during the Pre-Production or Production phases of the testing of the current release, which were resolved before the final deployment of the final production release. Finally these can be issues which were reported or found during the testing phase, but which have been closed without any action taken. 

Technical Updates

In addition to the Technical Updates reported in the following monthly Release Notes:

• • SNOMED CT February 2022 International Edition - SNOMED International Release notes
  • SNOMED CT March 2022 International Edition - SNOMED International Release notes
  • SNOMED CT April 2022 International Edition - SNOMED International Release notes
  • SNOMED CT May 2022 International Edition - SNOMED International Release notes
  • SNOMED CT June 2022 International Edition - SNOMED International Release notes
  • SNOMED CT July

• • 2022 International Edition - SNOMED International Release notes

 ...the following technical updates pertain to the NL Edition: 

Notice of changes to the NL Edition Release Package naming convention

Release Package naming convention standardised

From the September 2022 Release of the NL Edition onwards, the RF2 package naming convention will be standardised to bring it in line with the other extensions in the community, enabling better interoperability..  The format will therefore change from:

• • SnomedCT_Netherlands_EditionRelease_PRODUCTION_[date]T[time]Z.zip

...to the following:

• • SnomedCT_ManagedServiceNL_PRODUCTION_NL1000146_[date]T[time]Z.zip

So, for the September 2022 NL Edition Release, for example, the RF2 package would have originally been called:

• • SnomedCT_Netherlands_EditionRelease_PRODUCTION_20220930T120000Z.zip

...whereas from now on it will instead be called:

• • SnomedCT_ManagedServiceNL_PRODUCTION_NL1000146_20220930T120000Z.zip

Release File naming convention standardised

From the September 2022 Release of the NL Edition onwards, the File naming convention will be standardised to bring it in line with the other extensions in the community, enabling better interoperability.  The format will therefore change from:

• • [FileType]_[ContentType]_[ContentSubType]_[CountryCode]_[VersionDate].[FileExtension]

...to the following:

• • [FileType]_[ContentType]_[ContentSubType]_[CountryCode][CountryNamespace]_[VersionDate].[FileExtension]

So, for the September 2022 NL Edition Release, for example, the Concept file name would have originally been called:

• • sct2_Concept_Snapshot_NL_20220930.txt

...whereas from now on it will instead be called:

• • sct2_Concept_Snapshot_NL1000146_20220930.txt

Notice of changes to the International Edition Release Schedule

As you may already know SNOMED International have transitioned to a monthly delivery schedule for the International Edition of SNOMED CT. The move towards more frequent releases of SNOMED CT realizes several benefits, including:

• • The potential to be able to get content changes into the terminology in a shorter time frame.
  • The fostering of better interoperability, as a result of entities being able to consume release content that is more aligned with other organizations.
  • The prevention of circular dependencies that occur in longer projects, due to the move towards smaller, more manageable authoring projects.
  • More automated validation services, as a result of the inherent removal of the Alpha/Beta stages in the Release cycle.

Whilst most users will continue unaffected (as they can simply continue to download the releases every 6 months as always), this transition will necessarily involve a few changes to process/packages:

• • Delta files have been removed from both International and Managed Service release packages, including the Sweden Extension.  A Delta Generation service will be provided for those who need it. The Delta Generation Tool allows users to create their own Delta between two fixed release dates - you can find it here:
    • https://github.com/IHTSDO/delta-generator-tool/releases

• • The ICD-O/ICD-10 Maps will continue to be published in each Monthly International Edition release package (in line with that month's content) for the foreseeable future, unless we experience issues with the new process in Production, and they need to be removed at a later date.

The first monthly Release of the SNOMED CT International Edition was published on the 28th February 2022 with the Delta files having been removed, and therefore they have been removed from the NL Edition from the September 2022 Release onwards.

Please note - While the SNOMED CT International Edition is moving to monthly releases, the NL Edition of SNOMED CT will remain on the current bi-annual release schedule of March and September.

RF2 package format     

Similar to the International Edition, the NL Edition will follow the technical specifications for RF2 packaging 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

1 ...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 

2. ...files that just 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. 

 Changes to the Release Package

Since the last release, our SNOMED NRC has changed to a new authoring platform. This has necessitated a number of changes in our releases:

• • We now release only a single package with release files. This contains the entire Netherlands edition. We no longer publish the extension as a separate package.
  • The patient-friendly descriptions have been moved into the standard Dutch module. They can still be identified using the patient-friendly language reference set; there is no longer be a separate patient-friendly package or even a separate patient-friendly module.
  • Dutch and English descriptions and text definitions are now split in different files:
    • sct2_Description_Snapshot_NL_20220930.txt
    • sct2_Description_Snapshot_EN_20220930.txt
    • sct2_ TextDefinition _Snapshot_NL_20220930.txt
    • sct2_ TextDefinition _Snapshot_EN_20220930.txt
  • The simple reference sets are no longer contained in a single file, but in a separate file for each reference set. It is now easier to import a single reference set, but to import all reference sets requires reading multiple files.
  • An error was detected in the handling of UUIDs of the Module Dependency reference set (MDRS), which caused historical data that should have been limited to the FULL edition to appear in the SNAPSHOT. The error has been fixed retro-actively, which means the UUIDs in the FULL version of the MDRS, for previously published rows, have been changed. We deemed this a better solution than propagating the error, but please contact us if this change causes an issue for your import.

For those who previously relied on the package or moduleId to identify which terms are patient-friendly, please note that this approach must have given you incomplete results, and now produces no results at all. We urge you to start using the patient-friendly language reference set. More information can be found at https://www.nictiz.nl/standaardisatie/terminologiecentrum/referentielijsten/inbouwen-snomed-referentieset/, in the SNOMED CT Release File Specifications at http://snomed.org/rfsand in our how-to videos at https://www.nictiz.nl/standaardisatie/terminologiecentrum/trainingsaanbod/.

 Feedback

3.3 Technical Updates

In addition to the Technical Updates reported in the following monthly Release Notes:

• • SNOMED CT February 2022 International Edition - SNOMED International Release notes
  • SNOMED CT March 2022 International Edition - SNOMED International Release notes
  • SNOMED CT April 2022 International Edition - SNOMED International Release notes
  • SNOMED CT May 2022 International Edition - SNOMED International Release notes
  • SNOMED CT June 2022 International Edition - SNOMED International Release notes

 ...the following technical updates pertain to the US Edition: 

3.3.1  Advanced Notice of upcoming changes to the US Edition Release Package naming convention

From the March 2023 Release of the US Edition onwards, the RF2 package naming convention will be changing from:

• • SnomedCT_USEditionRF2_PRODUCTION_[date]T[time]Z.zip

...to the following:

• • SnomedCT_ManagedServiceUS_PRODUCTION_US1000124_[date]T[time]Z.zip

So, for the March 2023 US Edition Release, for example, the RF2 package would have originally been called:

• • SnomedCT_USEditionRF2_PRODUCTION_20230301T120000Z.zip

...whereas from now on it will instead be called:

• • SnomedCT_ManagedServiceUS_PRODUCTION_US1000124_20230301T120000Z.zip

3.3.2  Notice of changes to the US Edition Module Dependency Refset Specifications

There has been discussion on the Module Dependency Refset Specifications (MDRS) records regarding dependencies not being transitive, meaning that they cannot be inferred from a chain of dependencies. For example, if module-A depends on module-B and module-B depends on module-C, the dependency of module-A on module-C must still be stated explicitly. This has not been resolved by SNOMED International, as their recent deliberations regarding the possibility of changing the specifications to make MDRS records transitive have concluded that so far, the business case for doing so is not strong enough. Therefore, the US Edition of SNOMED CT still, in theory, has missing MDRS records which should explicitly call out the dependency of the ICD-10CM map module on both Core International modules. As the new automated MDRS functionality also generates these records, it was decided to allow their introduction until SNOMED International decides to change the RF2 specifications. These records have been included in the September 2022 US Edition release by allowing the automated MDRS generation code to add 2 new records to the US Edition MDRS, explicitly calling out the dependency of the ICD-10CM map module on both Core International modules:

• • > e37cecd9-329a-4bf2-96eb-befefd9c45c3    20220901    1    5991000124107    900000000000534007    900000000000207008    20220901    20220630
  • > 5b163b38-a5e6-4430-aaaa-82663c4bca4a    20220901    1    5991000124107    900000000000534007    900000000000012004    20220901    20220630

3.3.3 Notice of changes to the International Edition Release Schedule

As you may already know SNOMED International have transitioned to a monthly delivery schedule for the International Edition of SNOMED CT. The move towards more frequent releases of SNOMED CT realizes several benefits, including:

• • The potential to be able to get content changes into the terminology in a shorter time frame.
  • The fostering of better interoperability, as a result of entities being able to consume release content that is more aligned with other organizations.
  • The prevention of circular dependencies that occur in longer projects, due to the move towards smaller, more manageable authoring projects.
  • More automated validation services, as a result of the inherent removal of the Alpha/Beta stages in the Release cycle.

Whilst most users will continue unaffected (as they can simply continue to download the releases every 6 months as always), this transition will necessarily involve a few changes to process/packages:

• • Delta files have been removed from both International and Managed Service release packages, including the Sweden Extension.  A Delta Generation service will be provided for those who need it. The Delta Generation Tool allows users to create their own Delta between two fixed release dates - you can find it here:
    • https://github.com/IHTSDO/delta-generator-tool/releases

• • The ICD-O/ICD-10 Maps will continue to be published in each Monthly International Edition release package (in line with that month's content) for the foreseeable future, unless we experience issues with the new process in Production, and they need to be removed at a later date.

The first monthly Release of the SNOMED CT International Edition was published on the 28th February 2022 with the Delta files having been removed, and therefore they have been removed from the US Edition from the March 2022 Release onwards.

Please note - While the SNOMED CT International Edition is moving to monthly releases, the US Edition of SNOMED CT will remain on the current bi-annual release schedule of March and September.

3.3.4 RF2 package format     

Similar to the International Edition, the US Edition will follow the technical specifications for RF2 packaging 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

1 ...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 

2. ...files that just 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. 

and suggestions

We welcome questions, comments or suggestions to improve the quality, accuracy and usability of the SNOMED CT US Edition. Please send feedback to NLM Customer Support https://support.nlm.nih.gov/. NL Edition. Please send feedback to info@snomed.nl.