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Vocabulary Work Group | Maturity Level: 5 | Ballot Status: Trial Use |
4.2.1.0.1 Summary
Source | SNOMED CT is used in FHIR international standards and resources. SNOMED CT is owned, maintained and distributed by SNOMED International . SNOMED International is the organization which publishes the International Edition of SNOMED CT. SNOMED International Members may also distribute their own SNOMED CT National Edition, which contains the international release plus local extension content and derivatives. |
System | |
Version | Where a code system version is used, it should be specified as a URI that represents a specific SNOMED CT Edition published on a particular date (e.g. the International Edition or a National Edition, with a version date), following the SNOMED CT URI Specification (see note below) |
Code | The following SNOMED CT artifacts are valid in the code element for the http://snomed.info/sct namespace: Concept |
Identifiers are not valid as codes in FHIR, nor are other alternative identifiers associated with SNOMED CT Concepts. Note: when SNOMED CT terms must be exchanged, use the Description Id Extension. | |
Display | The correct display for a SNOMED CT concept is one of the |
terms associated with that concept. The best display is the preferred term in the relevant language or dialect, as specified in the associated language reference set |
. SNOMED CT synonyms may be case sensitive. |
SNOMED International does not define terms for expressions. If a SNOMED terminology producer publishes human-readable terms for expressions in an expression repository, this term may be used as the display. Similarly, if a SNOMED terminology producer publishes an official template for generating terms from an expression, a term generated using the template may be used as the display. If no term or description template has been published, the full expression with |
terms embedded may be used |
. Note that Display |
is not intended to contain terms entered by the user |
that have not been officially published by a SNOMED CT Terminology Producer. | |
Inactive | Inactive codes are identified using the 'inactive' property (see below). |
Subsumption | SNOMED CT Subsumption testing for concepts is based on the |is a| relationship defined by SNOMED CT. |
Filter Properties | Several filter properties are defined, as described below. |
This specification publishes a canonical SNOMED CT code system resource. See also the SNOMED CT Usage Summary.
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where [sctid] is the concept id that identifies the given SNOMED CT edition (based on the identifier of the most dependent module), and "YYYYMMDD" is the date of release. Examples of sctids that identify a specific edition areare listed here.
4.2.1.0.3 SNOMED CT Expressions
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In addition to the standard properties, the following properties are defined for SNOMED CT:
Property Name | Data Type | Comments |
inactive | boolean | Whether the code is active or not (defaults to false). This is derived from the active column in the Concept file of the RF2 Distribution (by inverting the value) |
sufficientlyDefined | boolean | True if the description logic definition of the concept includes sufficient conditions. This is derived from the definitionStatusId value in the Concept file of the RF2 distribution (i.e. If 900000000000073002 |Sufficiently defined concept definition status| then true). |
moduleId | code | The SNOMED CT concept id of the module that the concept belongs to. |
normalForm | string | Generated Necessary Normal form expression for the provided code or expression, with terms. See http://snomed. |
org/nnf | ||
normalFormTerse | string | Generated Necessary Normal form expression for the provided code or expression, conceptIds only. |
In addition, any SNOMED CT relationships, where the relationship type is subsumed by 410662002 |Concept model attribute|, also automatically become properties. Properties that represent SNOMED CT concept model attributes are referred to using their concept id, rather than their human readable term.
For example, the laterality property is represented using the conceptId for 410662002 |Laterality|:concept id '272741003', rather than the term 'laterality':
Property Name | Data Type | Comments |
272741003 | code | The value of the laterality attribute in the definition of the given code or expression. |
The equivalent URI for the Laterality property is |
Note that when a $lookup operation is performed on a SNOMED CT concept, servers SHALL return the full URI for the edition and version being used (see above) in the version
property. Other properties are at the discretion of the server and the client.
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We've added a new section for Expressions. Bringing other text on the page into line with SNOMED International's definition of what constitutes valid SNOMED CT compositional grammer, we've removed advice about including or not including text definitions - both are considered equally valid, although there may be an argument for including the orginal text selected by the end user.
SNOMED CT Properties
The following property has been removed since "NormalForm" covers this case in that SNOMED CT Expressions are considered valid with our without terms. These can be added or stripped out as required, locally and programmatically, for display purposes.
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New Sections - works in progress
These have been removed into their own pages while the text is agreed. Since they are additional guidance, there is no reason to think that anything being added will 'break' the above.
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