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 International Edition (published on the first day of the month) and the Extension (published on the last day of the month)

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 May 2025 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.

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 May 2025 International Edition - SNOMED International Release notes. 

Changes to the reference set file name format

The current naming format for the files containing reference sets includes the name of the reference set. This has led in some extensions to filenames that were too long. The SNOMED community has decided to change the name format to include the refsetId instead of the refset name. This change took effect in the January 2025 release. For more information, see section Technical updates  - Refset file naming conventions.

Changes to the release format of patient-friendly explanations

The SNOMED CT NL Edition contains two types of patient-friendly descriptions:

• The patient-friendly terms are synonyms for SNOMED concepts that are understood by most patients: i.e. not medical jargon. They are marked as preferred in the 15551000146102 |Patient-friendly Dutch language reference set|.
• The patient-friendly explanations are brief explanations of SNOMED concepts at reading level B1, which can be understood by approx. 80% of the Dutch population. Until now, these have been added to SNOMED as text definitions in the 160161000146108 |Patient-friendly Dutch at B1 reading level language reference set|. This has a serious drawback: text definitions must be unique in SNOMED, but not every concept can be uniquely explained in at most 4 sentences.

SNOMED has recently added a new component type to the RF2 specification: the annotation. We have decided that this is much more suited to the nature of a patient-friendly explanation. From the September 2024 edition onwards, patient-friendly explanations have been published as component annotations with typeId 480411000146103 |Explanation for patient| and languageDialectCode nl-NL. For details on the format, see 5.6. Component Annotation Reference Set and 5.2.4.8 Component Annotations String Value Reference Set.

This change does not affect the way in which patient-friendly terms and explanations are retrieved through the 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, including a manual, can be found at https://www.nictiz.nl/standaardisatie/terminologiecentrum/nationale-terminologieserver/ and https://github.com/terminologieserver.

Monthly releases 

The SNOMED NL edition is published 10 times per year: on the last day of every month excluding July and December. These frequent releases realize a number of 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.

On https://nictiz.nl/publicaties/dynamische-waardelijsten/ Nictiz has published a guide on how and when to update SNOMED and on how to deal with issues that arise from organisations using different versions. 

On https://nictiz.nl/wat-we-doen/activiteiten/terminologie/referentielijsten-2/ Nictiz publishes overviews of changes to reference sets, sorted by health care domain, for end users and application managers.

Content Development Activity 

Summary

The June 2025 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. 

June 2025 NL Edition of SNOMED CT Statistics 

These statistics include the content from the June 2025 International Edition and June 2025 NL Edition.

These statistics include new content from the June 2025 NL Extension.

SNOMED CT derived products 

New reference sets

Inactivated reference sets

Changed reference sets

For an overview of changes to existing reference sets, see https://nictiz.nl/wat-we-doen/activiteiten/terminologie/referentielijsten-2/.

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: 

Technical Updates

Core Technical Updates reported in the following monthly Release Notes:

SNOMED CT June 2025 International Edition - SNOMED International Release notes

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.

Refset File Naming conventions

The new naming conventions for additional reference sets files have been applied to the NL Edition release package from the January 2025 NL Managed Service Release onwards.  The new convention updates the file names to use RefsetID prefixes instead of the old human readable format, in order to improve maintainability and allow for machine reading of the file names.  However, this convention will ONLY be applied to additional refsets, and not core refsets such as Language refset, Association refset, MRCM refset files, etc. (as these were considered to incur too high an impact on end users if the naming conventions were to be changed)

So, for example, in the January 2025 NL Managed Service Release the additional refset file names have changed from:

• • der2_Refset_DutchOrdinalMicrobialSusceptibilityTestResultsSimpleRefsetSnapshot_NL1000146_20250131.txt   →    der2_Refset_140301000146101SimpleRefsetSnapshot_NL1000146_20250131.txt
  • der2_Refset_DutchCausativePathogensInCongenitalInfectionSimpleRefsetSnapshot_NL1000146_20250131.txt  →    der2_Refset_210051000146105SimpleRefsetSnapshot_NL1000146_20250131.txt
  • ...etc.

Please contact the Netherlands National Release Center via Nictiz Servicedesk for any further details, or if you need assistance with these improvements.

Feedback and suggestions

We welcome questions, comments or suggestions to improve the quality, accuracy and usability of the SNOMED CT NL Edition through the Nictiz Servicedesk.