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 Edition is a combination of the full January 2018 SNOMED CT International Edition and the US Extension of SNOMED CT. The US Edition eliminates the need for implementers to manually combine the US Extension and International releases.
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. SNOMED CT US Edition is developed and maintained by the United States National Library of Medicine 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).
This document provides a summarized description of the content changes included in the March 2018 release of the SNOMED Clinical Terms® US 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 2018 US Edition release.
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 2018 International Edition Release Notes.
2 Content Development Activity
The March 2018 SNOMED CT US Edition is the second 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.
In addition to the new content from the SNOMED CT January 2018 International Edition, this release includes content from prior versions of the US Extension as well as new content requested by US SNOMED CT users. 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 March 2018 US Extension of SNOMED CT Statistics
|New Concepts Added (total)||514|
|Concepts Moved to Core (this release)||0|
|Concepts Moved to Core (all time)||53|
|Concepts Promoted to Core (all time and not defaulted back to extension)||370|
|Concepts Defaulted to Core (this release)||0|
|Concepts Defaulted to Core (all time and not promoted back to extension)||0|
|Active concepts in US Extension||6209|
|Retired concepts in US Extension||397|
|Active Descriptions in US Extension||15816|
|Synonyms of International Edition Concepts||465|
|Active (inferred) relationships in US Extension||25847|
|Between of International Edition Concepts||77|
|Active (inferred IS A) relationships in US Edition||512688|
|Retired (inferred IS A) relationships in US Edition||364559|
2.2 Content Highlights
In addition to XXX new concepts specific for the US, the March 2018 SNOMED CT US Edition also contains all of the content from the January 2018 SNOMED CT International Edition. Approximately 200 requests for terminology inclusions and changes were submitted via US CRS. Additionally, this latest version of the US Edition includes new CMT content in the vascular procedures area.
2.3 SNOMED CT derived products
2.3.1 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_20180301.tsv) contained within the documentation folder in both the US Edition release and standalone download.
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_20180301.txt, which is in the Map folder under Refset in the Snapshot Release Type folder.
PLEASE NOTE: Starting with this 2018 March SNOMED CT US Edition (20180301) release, the SNOMED CT to ICD-10-CM map refset data will be maintained as per the SNOMED CT RF2 specifications. Because this is the first release where the map refset data are to be maintained, the 6011000124106 | ICD-10-CM complex map reference set (foundation metadata concept)| data are the same in the Full, Snapshot, and Delta releases. Going forward (starting with the 2018 September SNOMED CT US Edition, 20180901), new 6011000124106 | ICD-10-CM complex map reference set (foundation metadata concept) data will be found in the Delta, current status data in the Snapshot, and a historical record of the refset data in the Full Release.
Additional map refset information can be found in the SNOMED CT to ICD-10-CM Release Notes (doc_Icd10cmMapReleaseNotes_Current-en-US_US1000124_20180301.pdf) found in the Documentation folder, or online (link here). Technical information (doc_Icd10cmMapTechnicalSpecifications_Current-en-US_US1000124_20180301.pdf) for the map can also be found in the Documentation folder, or online (link here).
2.3.2 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_20180301.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  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 20140901.
2.3.3 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.
The Transitive Closure script is located in the TransitiveClosure file within the Resources file, tls2_TranstiveClosure_US1000124_20180301.pl. The Transitive Closure table is located in the TransitiveClosure file within the Resources file, res2_TransitiveClosure_US1000124_20180301.txt. 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. In addition to the known issues reported by the IHTSDO for SNOMED CT International Edition (SNOMED CT January 2018 International Edition - SNOMED International Release notes), the following are known issues for the SNOMED CT US Edition.
For the SNOMED CT Managed Service - US Edition September 2017, the following Known Issues were identified, and agreed to be resolved in the next editing cycle:
3.2 Technical Updates
In addition to the Technical Updates reported in the SNOMED CT January 2018 International Release, the following technical updates pertain to the US Edition:
3.2.1 Module Dependency References Set (MDRS) files re-modelled
The MDRS files in the US Extension and US Edition packages have been re-modelled, in order to resolve historical inaccuracies. The following changes have been implemented:
- The UUID's have been fixed, in order to correctly state the continuation of the dependencies
All invalid records were removed - this included both:
all of the extraneous inactivation records, plus
all of the duplicate active records
All dates corrected to identify valid dependencies
3.2.2 RF2 package naming convention
The naming convention as of the September 2017 US Edition zip file has changed to align with the July 2017 International Edition release naming. The July 2017 International Edition improved the RF2 package naming convention to align with the ISO8601 standard.
Previous convention: SnomedCT_USEditionRF2_Production_20170301T120000.zip
Going forward the US Edition zip package will be called: SnomedCT_USEditionRF2_PRODUCTION_20170731T120000Z.zip
3.2.3 Data Corrections
In the September 2017 US Edition release (20170901) the following rows were removed from the Full Release of SNOMED CT US Edition. This is an intentional fix for US concepts that were previously promoted to the International Core but had erroneously remained in the US maintained module.
3.2.4 Advanced Warning
As per the SNOMED International decision to inactivate the 159083000 |WAS A (attribute)| and stop updating the 900000000000528000 | WAS A association reference set (foundation metadata concept)| will take effect from the 20180301 US Edition release going forward. Additional information regarding the reason for inactivation and cessation of use of the association reference set can be found in the SNOMED CT January 2018 International Edition - SNOMED International Release notes.
3.2.5 Association Reference set naming convention
As per the SNOMED International decision to update and improve the Association Reference file, the March 2018 SNOMED CT US Edition has also updated the naming convention.
It will no longer be named using this convention:
Instead it will be named as follows:
Therefore, the three files in the March 2018 US Edition release package will be called:
3.3 Feedback 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/ics/support/default.asp?style=classic&deptID=28054&category=snomed_ct.
Draft Amendment History
|Andrew Atkinson||Initial draft created|
|Suzy Roy||Final Production updates|