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 NL Edition is a combination of the full June 2022 SNOMED CT International Edition and the 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 NL Edition is developed and maintained by the NL NRC and is available to authorized 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. 

Background

This document provides a summarized description of the content changes included in the March 2023 release of the SNOMED Clinical 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 March 2023 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 January 2023 International Edition - SNOMED International Release notes.

Changes to the release format

Preceding the previous release of September 2022, our SNOMED NRC changed to a new authoring platform. This 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. If you have already made these changes following the September release, then nu further action is required.

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 March 2023 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 January 2023 International Edition and the September 2022 March 2023 NL Edition.

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

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.

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. 

The following Resolved Issues for the SNOMED CT September 2022 NL Edition:

Technical Updates

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

• • SNOMED CT August 2022 International Edition - SNOMED International Release notes
  • SNOMED CT September 2022 International Edition - SNOMED International Release notes
  • SNOMED CT October 2022 International Edition - SNOMED International Release notes
  • SNOMED CT November 2022 International Edition - SNOMED International Release notes
  • SNOMED CT December 2022 International Edition - SNOMED International Release notes
  • SNOMED CT January 2023 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

Since the September 2022 Release of the NL Edition, the RF2 package naming convention has been standardised to bring it in line with the other extensions in the community, enabling better interoperability. The format has changed from:

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

to

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

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

• • SnomedCT_Netherlands_EditionRelease_PRODUCTION_20230331T120000Z.zip

But is now called:

• • SnomedCT_ManagedServiceNL_PRODUCTION_NL1000146_20230331T120000Z.zip

Release File naming convention standardised

Since the September 2022 Release of the NL Edition, the File naming convention has been standardised to bring it in line with the other extensions in the community, enabling better interoperability.  The format has changed from:

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

To:

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

So, for the March 2023 NL Edition Release, for example, the Concept file name would have originally been called:

• • sct2_Concept_Snapshot_NL_20230331.txt

But is now called:

• • sct2_Concept_Snapshot_NL1000146_20230331.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 NL Edition.  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 for now on the current bi-annual release schedule of March and September.

RF2 package format     

Similar to the International Edition, the NL Edition follows 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 September 2022 NL Edition release we have made one change to the release format:

• • The file der2_scRefset_CorrelatedMapTypeReferenceSetSnapshot_NL1000146_20220930 contains two mapping reference sets. These were of a Dutch type: 31441000146107 | Correlated map type reference set (foundation metadata concept)|. This type has now been replaced with the international type 1193542003 |Simple map with correlation from SNOMED CT type reference set (foundation metadata concept)|. The new reference set type has exactly the same number and type of columns. The sole difference is that the final column has header correlationId, where the old type had header snomedCtSourceCodeToTargetMapCodeCorrelationValue; however, the content of the column remains the same.

Between the March and September 2022 release, the Dutch SNOMED NRC has changed to a new authoring platform. This has necessitated a number of changes in our releases, which first took effect in September 2022:

• • 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_20230331.txt
    • sct2_Description_Snapshot_EN_20230331.txt
    • sct2_ TextDefinition _Snapshot_NL_20230331.txt
    • sct2_ TextDefinition _Snapshot_EN_20230331.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 and suggestions

We welcome questions, comments or suggestions to improve the quality, accuracy and usability of the SNOMED CT NL Edition. Please send feedback to info@snomed.nl.