By now, most healthcare organizations recognize the challenges associated with aggregating and sharing clinical information. It’s no secret that disparate health IT systems and clinical vocabularies create barriers to exchanging and using patient data in a meaningful way.
What is SNOMED CT and why is it important?
Systematized Nomenclature of Medicine Clinical Terms, commonly known as SNOMED CT®, is the most comprehensive, multilingual clinical terminology in the world, encompassing more than 300,000 concepts, along with terms, synonyms, and definitions for human and non-human concepts. In fact, it was specifically designed to be a U.S. standard for electronic health information exchange.
SNOMED CT clinical concepts are organized hierarchically and represented by multiple levels of granularity. Hierarchies include:
- Body Structure
- Clinical Finding
- Social Context
SNOMED CT comprises four files:
- Concept file: codes that identify unique objects
- Description file: terms that explain the concept
- Relationship file: lateral associations between related concepts
- Hierarchy file: vertical (hierarchical) structure
For example, the number representing the common cold may be linked to such descriptions as “common cold,” “acute coryza,” “acute infective rhinitis,” “cold,” or “head cold.”
History of SNOMED CT
Developed by the College of American Pathologists in 1974 as the Systemized Nomenclature of Pathology (SNOP), the current format—SNOMED CT— was released in 2002 as a combination of SNOMED RT (Reference Terminology) and CTV3 (Clinical Terms Version 3). The clinical vocabulary is now owned and maintained by the International Health Terminology Standards Development Organization (IHTSDO) and used in more than fifty countries. SNOMED CT is being used in conjunction with the World Health Organization as the foundation for ICD-11.
How SNOMED CT is used
SNOMED CT was specifically designed to be a U.S. standard for electronic health information exchange, as it is essential for recording and sharing clinical data such as patient problem lists and family, medical, and social histories in EHRs.
SNOMED CT was required by Stage 2 Meaningful Use for documenting problem lists. It remains an excellent tool today in achieving requirements put forth by Medicare and Medicaid's Promoting Interoperability Programs, as it is the foundation for storage, retrieval, and exchange of electronic health data. Its usefulness can be further leveraged through mapping to other international standards, such as ICD-9, ICD-10 or CPT to better facilitate semantic interoperability. For instance, when clinical terms are seamlessly mapped between ICD-9, ICD-10, and SNOMED CT, revenue cycle efficiency and accuracy are boosted by eliminating productivity losses that would be associated with trying to identify the correct code from ICD-10’s 155,000 options.
The complexities in maintaining SNOMED CT
With a complicated hierarchy and various editions, SNOMED CT is a challenging ontology to maintain and keep up to date. Let’s take a closer look at some of these complexities.
A polyhierarchical ontology
Part of the complexity is due to being a polyhierarchical ontology, meaning that the relationships between concepts and attributes contribute to the meaning of each concept, or that terms in the hierarchy of SNOMED CT can have more than one “parent”.
International and United States editions
The International Edition of SNOMED CT works in concert with the United States Edition, which is maintained by the National Library of Medicine (NLM). However, these editions are not released at the same time. Changes in the International Edition can disrupt some of the US Edition concepts until the latest US Edition is released, due to pending information needed regarding hierarchical positioning of concepts.
International Edition of SNOMED CT introduces monthly updates
SNOMED CT has announced that beginning in February 2022, it will move their release cycle from every six months (January and July), to monthly. The NLM has announced that its updates will remain at every six months, in March and September. While more frequent updates to the International Edition is a positive change, it can also mean a greater governance burden when these changes are applied.
Mapping across other standards
When mapped to other international standards, changes in concepts and terms in SNOMED can trigger the need for mapping changes. Changes to the other standard can also trigger the need to update maps as well.
Leveraging SNOMED CT across health IT systems
By standardizing the way health IT systems read disparate terminologies, SNOMED CT enables consistent representations and reproductions of clinical content in EHRs. Other applications can use SNOMED CT for clinical decision support systems, laboratory reporting, emergency room charting, and cancer reporting. To ensure that these systems can leverage all that SNOMED CT has to offer, it’s important to keep up-to-date with the latest releases, including mapping across other healthcare terminologies. Speaking of updates, see below for a summary of the latest changes.