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 July 2023 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 2024 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 2024 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 February 2024 International Edition - SNOMED International Release notes.

Changes to the release format

Preceding the September 2022 release, our SNOMED NRC changed to a new authoring platform. This necessitated a number of changes in our release. For details, please refer to sections 3.3 & 3.4 of the SNOMED CT Managed Service - Netherlands Edition Release Notes - September 2022. However, we failed at that time to describe the consequences for the National Terminology Server with respect to patient-friendly terms. Retrieving the patient-friendly term now requires a different query. For details, please read the following section on the National Terminology Server.

Preparation for monthly releases of the NL edition

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.

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.

Nictiz has received several requests to publish more frequently as well. We plan to publish monthly from October 2024 onwards – weather and tooling permitting. We will use the intervening seven months to:

• Streamline our internal processes to enable monthly releases.
• Gather a group of SNOMED stakeholders to discuss the consequences of monthly releases and agree on how to handle them.
• Formulate a release policy in accordance with Nictiz’ Duurzaam releasebeleid.
• Publish a guide on how and when to update SNOMED; and on how to deal with issues that arise from organisations using different versions.

We are looking for you as a stakeholder to give us insight into your needs and into the impact of this change on your business process. If you are willing to participate, please submit a request at the Nictiz Servicedesk with the subject Monthly SNOMED releases – stakeholder participation.

Patient-friendly terms and explanations

In 2023-2024 Nictiz and MedMij have run a pilot project Patiëntvriendelijke Termen, the aim of which was to establish a set of requirements for patient-friendly terms and explanations of SNOMED concepts, a process for their development and a tried and tested method of distribution. This has led to a small number of new explanations which are published in the March 2024 release. More importantly, it has caused us to evaluate the release format for patient-friendly terms and explanations. We believe that a number of changes are necessary:

• We currently have two language reference sets for patient-friendly terms: one on B1 reading level and another which does not specify reading level. One of the project outcomes is that all explanations should have a reading level of B1 at most. As in future all explanations will be at B1 reading level, there is no reason to keep the distinction in reference sets. Thus:
  • 160161000146108 | Patient-friendly Dutch at B1 reading level language reference set| will be retired starting September 2024.
  • Any patient-friendly terms in the Patient-friendly Dutch at B1 reading level language reference set| that are not at B1 reading level will be retired.
• At present, patient-friendly explanations are added to SNOMED concepts as text definitions in a patient-friendly language reference set. This is misleading, as the explanations are in no way definitions: they are not unique to the concept and do not fully represent it. It also causes difficulties in maintenance. Therefore:
  • All text definitions in both patient-friendly language reference sets will be retired.
  • We will publish a separate file through MLDS that contains explanations with a UUID to identify them.
  • To SNOMED concepts we will add an Annotation of type Consumer explanation whose value is the UUID of an explanation.

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.

Content Development Activity 

Summary

The March 2024 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. 

March 2024 NL Edition of SNOMED CT Statistics 

These statistics include the content from the February 2024 International Edition and March 2024 NL Edition.

These statistics include new content from the March 2024 NL Extension.

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: 

Technical Updates

Core Technical Updates reported in the following monthly Release Notes:

• • https://confluence.ihtsdotools.org/display/RMT/SNOMED+CT+September+2024+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.

Changes to the Identifier file format

In line with the proposals documented here:  https://confluence.ihtsdotools.org/mag/snomed-international-proposal-to-change-the-rf2-identifier-file-specification - the Netherlands Edition Release will from now on include the following changes to the format of the Identifier files:

• • • < identifierSchemeId    alternateIdentifier    effectiveTime    active    moduleId    referencedComponentId           ...to
    • > alternateIdentifier    effectiveTime    active    moduleId    identifierSchemeId    referencedComponentId

These improvements were introduced in the September 2023 Netherlands Edition release, and will be used in all future Netherlands Edition releases until further notice.

Notice of changes to the NL Extension Release package

In line with the refined implementation of Annotations, we are updating all Extensions in order to align them with the updated version of the refsets in the International Edition Release package (which were first published in June 2024).

The languageCode field was specified as the two characters of ISO-639-1 code for the language of the annotation text. The change includes support for specifying dialect when it is applicable by adhering to RFC 5646, which allows the combination of two characters of ISO 639-1 code and two uppercase letters of country code (ISO 3166) separated by a hyphen.  The changes apply to both the Member Annotations String Value Reference Set + Component Annotation String Value reference set:

• • The column "languageCode" has therefore been changed to "languageDialectCode".
    • Component Annotations (1292992004)
      • OLD:    id    effectiveTime    active    moduleId    refsetId    referencedComponentId    languageCode    typeId    value
      • NEW:   id    effectiveTime    active    moduleId    refsetId    referencedComponentId    languageDialectCode    typeId    value
    • Member Annotations (1292995002)
      • OLD:   id    effectiveTime    active    moduleId    refsetId    referencedComponentId    referencedMemberId    languageCode    typeId    value
      • NEW:  id    effectiveTime    active    moduleId    refsetId    referencedComponentId    referencedMemberId    languageDialectCode    typeId    value

Feedback and suggestions

We welcome questions, comments or suggestions to improve the quality, accuracy and usability of the SNOMED CT NL Edition. Please submit a request at the Nictiz Servicedesk.