This page is part of the FHIR Specification (v1.2.0: STU 3 Draft). The current version which supercedes this version is 5.0.0. For a full list of available versions, see the Directory of published versions . Page versions: R4B R4 R3 R2

• Using Codes
• Code Systems
• Value Sets
• v2 Tables
• v3 Namespaces
• Concept Maps
• Identifier Systems

1.25.1.1 Using SNOMED CT with FHIR

Vocabulary Work Group

Maturity Level: N/A

Ballot Status: DSTU 2

1.25.1.1.1 Summary

Source	SNOMED CT is made managed by IHTSDO . IHTSDO is an international standards organization with multiple different countries as members, each of which distribute their own variant of SNOMED CT
System	The URI http://snomed.info/sct identifies the SNOMED CT code system
Version	Where a version is used, it should be a full URI that represents the specific distribution, 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 IDs , Expressions (grammar ) and SNOMED Legacy codes . Description Ids are not valid, nor are other concepts associated with SNOMED CT Concepts using the RF2 identifier infrastructure. Expressions SHOULD NOT contain terms, only concept IDs
Display	The correct display for a SNOMED CT concept is one of the preferred terms for the concept. Preferred terms are case sensitive. The Fully Specified Name is not an appropriate choice. The source of preferred name comes from a Language Reference Set. SNOMED CT does not define displays for expressions; if no display has been associated with the expression through a value set or other mechanism, the full expression syntax with preferred terms embedded may be used
Filter Properties	Several properties are defined as described below

Note: The IHTSDO glossary explains some of these SNOMED CT specific terms.

1.25.1.1.2 Version Issues

There is no single distribution that contains all defined SNOMED CT codes in all contexts of use; instead, each national office distributes a set of version of a particular distribution. In addition, other release authorities may be designated. The SNOMED CT URI Specification describes how to unambiguously reference a particular version of a distribution:

  http://snomed.info/sct/[sctid]/version/[YYYYMMDD] 

where [sctid] is the concept id of the SNOMED CT distribution (e.g. 32506021000036107 for Australia), and the tail is the date of release (by custom, this is usually the last day of the month). Note that many implementations are in the habit of simple using the date of release in the form YYYYMMDD (e.g. "20140531"), and assuming that the distribution is known. However this is not always safe, so implementations that populate the version element SHOULD use the full URI form.

1.25.1.1.3 Copyright/License Issues

The use of SNOMED CT codes, display names and value sets in this specification is subject to (basis to be confirmed). This does not convey the right to use SNOMED CT to any users of this specification; implementers must acquire a license to use SNOMED CT in their own right (from their national SNOMED CT authority, or elsewhere).

Note that the US distribution of SNOMED CT is currently used as the underlying system for the FHIR specification.

1.25.1.1.4 SNOMED CT Filter Properties

This section documents the property filters that can be used with the SNOMED CT code system in value set composition statements.

For implementer convenience, some of the property filters are documented in terms of the SNOMED CT Query Language , but this does not imply that its use is required. To Do: what's the correct link for this>

1.25.1.1.4.1 By Subsumption

DescendentsAndSelf([concept])

1.25.1.1.4.2 By Reference Set

MembersOf([concept])

1.25.1.1.4.3 By Snomed Query Expression

1.25.1.1.4.4 By whether post-coordination is allowed

n/a

1.25.1.1.5 Implicit Value Sets

Implicit value sets are those whose specification can be predicted based on the grammar of the underlying code system, and the known structure of the URL that identifies them. SNOMED CT has two sets of implicit value sets: By Subsumption, and By Reference Set.

If any value set resources exist with an identifier that conforms to the URL patterns specified below, the content of the resource must conform to the template provided. Profiles and other value set references are allowed to reference these value sets directly (by reference as a URI, rather than by a value set reference, which is a literal reference).

A SNOMED CT implicit value set URL has two parts:

• the base URL is either "http://snomed.info/sct", or the URI for the edition version, in the format specified by the IHTSDO the SNOMED CT URI Specification
• a query portion that specifies the scope of the content

"http://snomed.info/sct" should be understood to mean an unspecified edition/version. This defines an incomplete value set whose actual membership will depend on the particular edition used when it is expanded.

For the second part of the URL (the query part), the 3 possible values are:

• ?fhir_vs - all Concept IDs in the edition/version. If the base URI is http://snomed.info/sct, this means all possible SNOMED CT concepts
• ?fhir_vs=isa/[sctid] - all concept IDs that are subsumed by the specified Concept.
• ?fhir_vs=refset/[sctid] - all concept IDs in the specified reference set

A value set with an identifier that follows the pattern "[edition/version]?fhir_vs=isa/[sctid]" in the identifier follows this template:

<ValueSet xmlns="http://hl7.org/fhir">
  <text>
    <status value="generated"/>
    <div xmlns="http://www.w3.org/1999/xhtml">
     [Some HTML that describes this value set as all concepts subsumed by conceptid]
    </div>
  </text>
  <identifier value="[edition/version]?fhir_vs=isa/[sctid]"/>
  <version value="[edition/version]"/>
  <name value="SNOMED CT Concept [conceptid] and descendents"/>
  <description value="All SNOMED CT concepts for [concept id or preferred description]"/>
  <copyright value="This value set includes content from SNOMED CT, which is copyright © 2002+ International Health Terminology Standards Development Organisation (IHTSDO), and distributed by agreement between IHTSDO and HL7. Implementer use of SNOMED CT is not covered by this agreement"/>
  <status value="active"/>
  <compose>
    <include>
      <system value="http://snomed.info/sct"/>
      <filter>
        <property value="concept"/>
        <op value="is-a"/>
        <value value="[sctid]"/>
      </filter>
    </include>
  </compose>
</ValueSet>

A value set with an identifier that follows the pattern "[edition/version]?fhir_vs=refset/[sctid]" in the identifier follows this template:

<ValueSet xmlns="http://hl7.org/fhir">
  <text>
    <status value="generated"/>
    <div xmlns="http://www.w3.org/1999/xhtml">
     [Some HTML that describes this value set as all concepts in the reference set identified by conceptid]
    </div>
  </text>
  <identifier value="[edition/version]?fhir_vs=refset/[sctid]"/>
  <version value="[edition/version]"/>
  <name value="SNOMED CT Reference Set [conceptid]"/>
  <description value="All SNOMED CT concepts in the reference set [concept id or preferred description]"/>
  <copyright value="This value set includes content from SNOMED CT, which is copyright © 2002+ International Health Terminology Standards Development Organisation (IHTSDO), and distributed by agreement between IHTSDO and HL7. Implementer use of SNOMED CT is not covered by this agreement"/>
  <status value="active"/>
  <compose>
    <include>
      <system value="http://snomed.info/sct"/>
      <filter>
        <property value="concept"/>
        <op value="in"/>
        <value value="[conceptid]"/>
      </filter>
    </include>
  </compose>
</ValueSet>