SNOMED Core Structures 2 nd AAHA Software Vendors Summit – April 21, 2009

Terminology of Terminology Concept embodiment of a particular meaning Really a “virtual” element in the system The string in concepts table is a member of the related list of descriptions. Description Any string used to represent a concept Relationship (in SNOMED) an object – attribute – value triple connecting two concepts through an attribute Relationships in SNOMED are explicit rather than implicit (as was the case in SNOMED III)

Terminology of Terminology Extension (valid) SNOMED content outside of SNOMED core but integrated such that it can be queried as if it were part of SNOMED core. An official extension is created by an organization that holds a namespace identifier (more later). Subset A functional subset of SNOMED is a list of concepts extracted from core, an extension or both to serve a defined purpose. Navigational subset A SNOMED subset that includes adequate hierarchical information to allow navigation (browsing).

SNOMED Core Concepts Table Each row in this table represents a medical concept. Descriptions Table Each row in this table specifies a term that can be applied to describe a single clinical concept. Relationships Table Each row in this table specifies a relationship between two clinical concepts. The nature of each relationship is represented using a special kind of clinical concept.

SNOMED Core A concept is described by the term (string) in 2-n descriptions At least the Fully Specified Name (FSN) + Preferred Term Each description refers to (only) 1 concept.

SNOMED Core A concept is the source of 1-n relationships (except the root concept). A concept is the target of 1-n relationships. A concept represents the type of relationship. A relationship refers to 3 concepts: a source, a target, and a relationship type.

Concepts Table Fields Key Fields ConceptIdThe unique SNOMED Clinical Terms Identifier for this Concept. Data Fields ConceptStatusThe status of a Concept indicates whether it is in active use and, if not, indicates the reason for withdrawal from current use. FullySpecifiedNameA unique phrase that describes a Concept in a way that is intended to be unambiguous. CTV3IDThe Read Code for this Concept. SNOMEDIDThe current SNOMED identifier for this Concept. IsPrimitiveIndicates whether a Concept is Primitive or Fully defined by its current set of Defining characteristics.

Descriptions Table Key Fields DescriptionId The unique SNOMED CT Identifier for this Description. Data Fields DescriptionStatus The status of a Description indicates whether it is in active use and, if not, indicates the reason for withdrawal from current use. ConceptId The unique SNOMED CT Identifier of the associated Concept. (Foreign key to Concepts Table). Term The text of a Term used to describe the associated Concept. InitialCapitalStatus An indication of whether the capitalization status of the first character of the Term is significant. DescriptionType An indication of whether the Term is the Fully Specified Name, Preferred Term or Synonym for the Concept to which this Description applies. LanguageCode An indication of a Language or Dialect in which this Description is valid. The language or dialect subset ultimately defines the descriptions for each concept.

Concepts -> Descriptions D2-0007FPneumonia (concept) 2Synonym In Local Extension xxxxxxzzz11x 2Synonym in NAHLN Extension xxxxxxyyy11x 2Synonym in Core xxxxxx01x 1Pneumonia Pneumonia (Disorder) = “preferred” description (term) – preferred by SNOMED, perhaps not your users 2 = synonym (alternate) 3 = fully specified name

Component History Table (future use) Key Fields ComponentIDThe unique SNOMED CT Identifier for the changed Component. ReleaseVersionThe version of SNOMED CT in which this change was made. Data Fields ChangeTypeAn indication of the nature of the change. StatusThe status of this Component after the change. ReasonAn optional text Description of the reason for the change.

Historical Relationships Key Fields RelationshipId The unique SNOMED CT Identifier of this Relationship. Data Fields ConceptId1 The unique SNOMED CT Identifier of the Concept which is the source of this Relationship. RelationshipType The unique SNOMED CT Identifier of the Concept which represents the type of relationship between the related Concepts. ConceptId2 The unique SNOMED CT Identifier of the Concept which is the target of this Relationship. CharacteristicType An indication of whether a Relationship specifies a defining characteristic of the source Concept or a possible qualifying characteristic of that Concept. Refinability An indication of whether it is possible to refine the target Concept when this relationship is used as a template for clinical data entry. RelationshipGroup An integer value that links together Relationships which are part of a logically associated Relationship group.

Historical Relationships Allowed attribute values SAME AS (redundant) MAYBE A (ambiguous - 2 or more) REPLACED BY (major changes) WAS A (IS A no longer valid) MOVED TO (namespace change) MOVED FROM (namespace change)

Relationships Table Key Fields RelationshipIdThe unique SNOMED CT Identifier of this Relationship. Data Fields ConceptId1The unique SNOMED CT Identifier of the Concept which is the source of this Relationship. RelationshipTypeThe unique SNOMED CT Identifier of the Concept which represents the type of relationship between the related Concepts. ConceptId2The unique SNOMED CT Identifier of the Concept which is the target of this Relationship. CharacteristicTypeAn indication of whether a Relationship specifies a defining characteristic of the source Concept or a possible qualifying characteristic of that Concept. RefinabilityAn indication of whether it is possible to refine the target Concept when this relationship is used as a template for clinical data entry. RelationshipGroupAn integer value that links together Relationships which are part of a logically associated Relationship group.

Concept -> Relationship Concept ID Relationship ID Concept ID Relationship Table Fracture (morphology) M Associated Morphology G-C Fracture of Femur DD Concept Name SNOMED ID SCT ID Concepts Table

SCTID The SCTID data type is a 64-bit integer, which is subject to the following constraints: Only positive integer values are permitted. The minimum permitted value is 100,000 (6 digits) The maximum permitted value is 999,999,999,999,999,999 (18-digits). As result of rules for the partition-identifier and check-digit, many integers within this range are not valid SCTIDs.

SCTID The SCTID does not contain semantic information related to the meaning of a concept or term It does however have a structure that is designed to allow different types of terminological components to be recognized. The nature of a component can be derived from the table in which a component is distributed. Partitioning the SCTID avoids reuse of the same identifier for a different type of component – thus avoiding ambiguity. This also allows the nature of the identifier to be recognized when stored in a record or transferred in a message.

SCTID SCTID for centrally distributed component.

SCTID SCTID for a component in an extension.

SCTID Partition Values 00A concept 01A description 02A relationship 03A subset 04A Cross Map set 05A Cross Map target 10A concept in an extension 11A description in an extension 12A relationship in an extension 13A subset in an extension 14A Cross Map set in an extension 15A Cross Map target in an extension