SNOMED Clinical Terms is a systematically organized computer processable collection of medical terms providing codes, terms, synonyms and definitions used in clinical documentation and reporting. SNOMED CT is considered to be the most comprehensive, multilingual clinical healthcare terminology in the world. The primary purpose of SNOMED CT is to encode the meanings that are used in health information and to support the effective clinical recording of data with the aim of improving patient care. SNOMED CT provides the core general terminology for electronic health records. SNOMED CT comprehensive coverage includes: clinical findings, symptoms, diagnoses, procedures, body structures, organisms and other etiologies, substances, pharmaceuticals, devices and specimens.
SNOMED CT is maintained and distributed by SNOMED International, an international non-profit standards development organization, located in London, UK. SNOMED International is the trading name of the International Health Terminology Standards Development Organization (IHTSDO), established in 2007.
SNOMED CT provides for consistent information interchange and is fundamental to an interoperable electronic health record. It provides a consistent means to index, store, retrieve, and aggregate clinical data across specialties and sites of care. It also helps in organizing the content of electronic health records systems by reducing the variability in the way data are captured, encoded and used for clinical care of patients and research. SNOMED CT can be used to directly record clinical details of individuals in electronic patient records. It also provides the user with a number of linkages to clinical care pathways, shared care plans and other knowledge resources, in order to facilitate informed decision-making, and to support long-term patient care. The availability of free automatic coding tools and services, which can return a ranked list of SNOMED CT descriptors to encode any clinical report, could help healthcare professionals to navigate the terminology.
SNOMED CT is a terminology that can cross-map to other international standards and classifications. Specific language editions are available which augment the international edition and can contain language translations, as well as additional national terms. For example, SNOMED CT-AU, released in December 2009 in Australia, is based on the international version of SNOMED CT, but encompasses words and ideas that are clinically and technically unique to Australia.
SNOMED CT consists of four primary core components:
- Concept Codes – numerical codes that identify clinical terms, primitive or defined, organized in hierarchies
- Descriptions – textual descriptions of Concept Codes
- Relationships – relationships between Concept Codes that have a related meaning
- Reference Sets – used to group Concepts or Descriptions into sets, including reference sets and cross-maps to other classifications and standards.
SNOMED CT “Concepts” are representational units that categorize all the things that characterize healthcare processes and need to be recorded therein. In 2011, SNOMED CT included more than 311,000 concepts, which are uniquely identified by a concept ID, e.g. the concept 22298006 refers to Myocardial infarction. All SNOMED CT concepts are organized into acyclic taxonomic (is-a) hierarchies; for example, Viral pneumonia IS-A Infectious pneumonia IS-A Pneumonia IS-A Lung disease. Concepts may have multiple parents, for example Infectious pneumonia is also a child of Infectious disease. The taxonomic structure allows data to be recorded and later accessed at different levels of aggregation. SNOMED CT concepts are linked by approximately 1,360,000 links, called relationships.
Concepts are further described by various clinical terms or phrases, called Descriptions, which are divided into Fully Specified Names (FSNs), Preferred Terms (PTs), and Synonyms. Each Concept has exactly one FSN, which is unique across all of SNOMED CT. It has, in addition, exactly one PT, which has been decided by a group of clinicians to be the most common way of expressing the meaning of the concept. It may have zero to many Synonyms. Synonyms are additional terms and phrases used to refer to this concept. They do not have to be unique or unambiguous.
SNOMED CT can be characterized as a multilingual thesaurus with an ontological foundation. Thesaurus-like features are concept–term relations such as the synonymous descriptions “Acute coryza”, “Acute nasal catarrh”, “Acute rhinitis”, “Common cold” (as well as Spanish “resfrío común” and “rinitis infecciosa”) for the concept 82272006.
Under ontological scrutiny, SNOMED-CT is a class hierarchy (with extensive overlap of classes in contrast to typical statistical classifications like ICD). This means that the SNOMED CT concept 82272006 defines the class of all the individual disease instances that match the criteria for “common cold” (e.g., one patient may have “head cold” noted in their record, and another may have “Acute coryza”; both can be found as instances of “common cold”). The superclass (Is-A) Relation relates classes in terms of inclusion of their members. That is, all individual “cold-processes” are also included in all superclasses of the class Common Cold, such as Viral upper respiratory tract infection (Figure).
As of 2011, SNOMED CT content limits itself to a subset of the EL++ formalism, restricting itself to the following operators:
- Top, bottom
- Primitive roles and concepts with asserted parent(s) for each
- Concept definition and conjunction but NOT disjunction or negation
- Role hierarchy but not role composition
- Domain and range constraints
- Existential but not universal restriction
- A restricted form of role inclusion axiom (xRy ^ ySz => xRz)
- The logic will be extended in the near future to include General Concept Inclusion Axioms.
For understanding the modelling, it is also important to look at the stated view of a concept versus the inferred view of the concept. In further considering the state view, SNOMED CT used in the past an modelling approach referred to as ‘proximal parent’ approach. After 2015, a superior approach called “proximal primitive parent” has been adopted.
SNOMED CT is used in a number of different ways, some of which are:
- It captures clinical information at the level of detail needed for the provision of healthcare
- Through sharing data it can reduce the need to repeat health history at each new encounter with a healthcare professional
- Information can be recorded by different people in different locations and combined into simple information views within the patient record
- Use of a common terminology decreases the potential for differing interpretation of information
- Electronic recording in a common way reduces errors and can help to ensure completeness in recording all relevant data
- Standardised information makes analysis easier, supporting quality, cost effective practice, research and future clinical guideline development
- A clinical terminology allows a health care provider to identify patients based on specified coded information, and more effectively manage screening, treatment and follow up
More specifically, the following sample computer applications use SNOMED CT:
- Electronic Health Record Systems
- Computerized Provider Order Entry CPOE such as E-Prescribing or Laboratory Order Entry
- Catalogues of clinical services; e.g., for Diagnostic Imaging procedures
- Knowledge databases used in clinical decision support systems (CDSS)
- Remote Intensive Care Unit Monitoring
- Laboratory Reporting
- Emergency Room Charting
- Cancer Reporting
- Genetic Databases
The above is a brief about SNOMED CT. Watch this space for more updates on the latest trends in Technology.