The Language of Healthcare: Exploring US Extension of SNOMED CT
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Welcome back to our blog series on essential healthcare terminologies that are transforming data management and patient care. So far, we’ve covered SNOMED CT - a comprehensive standard for clinical terminology, ICD-10-CM - a vital classification system for coding health conditions and procedures and LOINC - a universal standard for identifying health measurements, observations, and documents. This week, we will explore SNOMED CT a bit further, investigating the usage of extensions within SNOMED CT.
In this post, we will use the US Extension of SNOMED CT as our example. We will go over the need for having the US Extension, compare it to the SNOMED Core, and understand its governance.
Don’t forget to explore TermHub’s public US Extension of SNOMED CT project to get hands-on experience with this extension. Stay with us throughout this series as we continue to unpack the healthcare terminologies that matter most. Follow TermHub on LinkedIn to get timely insights that can help you stay at the forefront of healthcare data management.
What is a SNOMED CT Extension?
A SNOMED CT Extension is a formal add-on to the international SNOMED CT clinical terminology (also known as SNOMED Core). It allows organizations, such as countries, regions, or specialist groups, to add concepts, descriptions, and relationships specific to their local needs while maintaining compatibility with the main SNOMED CT standard. This allows such organizations to have interoperability of their local data as long as the system already supports SNOMED Core.
Below are the key points that define a SNOMED CT Extension:
A Formal SNOMED Construct
Extensions are governed by SNOMED International rules and align with the official SNOMED CT data structures. As the organization updates these rules and data structures, extensions are expected to follow the same quality, technical, and editorial guidelines.
Uses Identical Data Model
Just like the core, extensions use the same Relationships, Concepts, and Descriptions model as well as the same ways of representing history. This ensures consistency and interoperability across all SNOMED CT–based systems.
Differentiated by moduleId
Each extension is distinguished by a unique moduleId, which helps keep extension content separate from the SNOMED Core and any other local extensions. Such information defines the content governance. The moduleId of a given component is listed in RF2, APIs, and most browsers.
US Extension concept with Module Id highlighted. See how the module id is defining the concept’s owner as US Extension rather than SNOMED Core.
Can Have Multiple Levels of Extensions
Organizations can build extensions on top of other extensions, creating multiple layers. For example, a national extension can serve as a “base” for a local extension, all while retaining interoperability with the SNOMED Core.
This is the case for the US Extension:
Uses SNOMED Core as Base Extension for local purposes.
Acts as the Base Extension for many US-based organizations such as:
Veterans Health Administration
Kaiser Permanente
Extensions vs Editions
An “Edition” bundles an extension with the international SNOMED Core (and possibly other extensions). This makes it easier to distribute and use a customized version of SNOMED CT that includes both the core and the additional extension concepts. Thus, one might refer to the:
US Extension of SNOMED CT: This strictly contains the content with the US Extension’s moduleId.
US Edition of SNOMED CT: This contains both the US Extension and the SNOMED Core bundled together.
Why do I need a US Extension to SNOMED CT?
The SNOMED CT US Extension is essential because the content found in the SNOMED CT International Edition (SNOMED Core) may not fully address the specific clinical, administrative, and regulatory requirements unique to the United States.
Here are the key reasons for its existence:
Addressing US Specific Clinical Needs
The International Edition might lack terms or concepts frequently used in US healthcare settings, such as terminology for localized conditions, treatments, or protocols. However, US healthcare organizations and systems must exchange this data seamlessly across diverse settings. The US Extension supports this effort by including content that aligns with local clinical practices, ensuring improved data exchange and interoperability within the US.
Supporting US Standards and Reporting
The US healthcare system relies on specific coding systems like ICD-10-CM, CPT, and LOINC for billing, reporting, and regulatory compliance. The US Extension provides mappings to these standards, ensuring SNOMED CT can integrate seamlessly into US healthcare workflows.
Reflecting Regional Language and Preferences
Clinical language can vary by country and even regionally within the US. The US Extension adds terms and synonyms that reflect US clinical language, making SNOMED CT more practical and user-friendly for US clinical providers.
What type of content is contained within the SNOMED CT US Extension?
The SNOMED CT US Extension contains content tailored to meet the unique requirements of healthcare delivery and reporting in the United States.
This includes:
Additional Concepts
Concepts not present in the International Edition but needed for US healthcare, such as specific clinical conditions, procedures, or terminologies. Some of these may eventually be moved to the International Edition in future releases. The extension also includes US-specific clinical or administrative concepts.
Descriptions
US-specific synonyms or preferred terms for existing international concepts as well as alternate descriptions to reflect common language or usage in US clinical practice. This helps ensure SNOMED CT is more intuitive and user-friendly for healthcare providers in the US.
Relationships
Modifications or additions to relationships between concepts to support US use cases. This enables a more accurate and relevant representation of medical knowledge within the US clinical context.
Mappings
Links to US-specific standards, such as ICD-10-CM, CPT (Current Procedural Terminology), and other coding systems for billing, reporting, or analytics. These mappings facilitate the integration of the US Extension of SNOMED CT with other widely-used coding systems in the US.
Reference Sets
Reference sets specific for SNOMED CT use within the US. These include predefined groups of concepts that meet specific US clinical and administrative needs.
Who maintains the SNOMED CT US extension?
The SNOMED CT US Extension is maintained by the National Library of Medicine (NLM), a division of the National Institutes of Health (NIH). The NLM oversees the United States-specific modifications and extensions to the SNOMED CT standard. The NLM ensures it aligns with national healthcare requirements and standards, and that it meets the unique healthcare requirements, regulatory frameworks, and clinical practices in the United States. This includes ensuring that US healthcare systems can use SNOMED CT effectively in ways that align with both national standards and local practices.
The NLM provides access to the SNOMED CT US extension via its Unified Medical Language System (UMLS) Metathesaurus, which integrates a wide array of biomedical terminologies and standards. This enables interoperability across a broad range of healthcare information systems, ensuring that SNOMED CT can be used in conjunction with other essential coding systems and terminologies that support clinical decision-making, administrative reporting, and regulatory compliance.
How often is the SNOMED CT US Extension updated?
The SNOMED CT US Extension is updated biannually, with releases typically occurring in March and September.
These updates align with the old biannual release cycle of the SNOMED CT International Edition, which prior to being released monthly, was updated twice a year (in January and July).
The updates incorporate:
New or updated content from the International Edition, including revised terminology or concepts that have been globally accepted.
Additions or modifications specific to US healthcare requirements, such as new concepts, descriptions, and mappings for emerging diseases, medical procedures, and US regulatory requirements.
Ongoing maintenance to ensure continued compatibility with evolving US healthcare standards, regulatory frameworks, and clinical practice guidelines..
The updated content is made available through the Unified Medical Language System (UMLS), authorized distribution channels such as the National Library of Medicine’s website, and other licensed data providers.
How do I request content in the SNOMED CT US Extension?
To request new content or modifications in the SNOMED CT US Extension, you can follow these steps:
Identify Your Need
Clearly define the concept, term, or relationship you want added or modified and ensure the requested content is not already available in the SNOMED CT International Edition or US Extension. For batch requests, you will need to use a special template that you can download here.
Submit a Request
Use the US SNOMED CT Content Request Service (USCRS) provided by the SNOMED International. Access via the website: https://us-request.ihtsdotools.org/.
Provide Detailed Information
Include details such as:
Description(s) of the concept or term.
Its intended use (e.g., clinical documentation, reporting, billing).
Supporting references or evidence, such as clinical guidelines or standards.