Guidance

Introduction

Aimed at FHIR developers, this guidance will show how to process the CodeableConcept, including:

  • How to populate the code
  • How to receive the code
  • How to render the code to a user
  • How to deal with multiple codes
  • What to do if the coded data is not understood by receiving systems

Description of elements (in terms of SNOMED CT)

Element Description
code The wrapper element for the CodeableConcept.
code.coding The wrapper element for the coded part of the CodeableConcept.
code.coding.extension.url The HL7 core-defined extension for providing the SNOMED CT Description ID for the display.
Value = http://hl7.org/fhir/StructureDefinition/coding-sctdescid
code.coding.extension.valueId
Where extension.url = http://hl7.org/fhir/StructureDefinition/coding-sctdescid		 The SNOMED CT Description Id for the display.
code.coding.extension.url A UK Core extension for providing a specific SNOMED CT Description display.
Value = https://fhir.hl7.org.uk/StructureDefinition/Extension-UKCore-CodingSCTDescDisplay
code.coding.extension.valueString
Where extension.url = https://fhir.hl7.org.uk/StructureDefinition/Extension-UKCore-CodingSCTDescDisplay		 The user selected SNOMED CT Description synonym, where this is different to the SNOMED CT Description preferred term.
code.coding.system Holds the SNOMED CT system identifier http://snomed.info/sct
code.coding.version Not used for SNOMED CT.
code.coding.code Holds the SNOMED CT Concept identifier.
code.coding.display Holds the SNOMED CT Concept preferred term.
code.coding.userSelected Indicates that this concept was chosen by the user.
code.text A plain text representation of the concept.

Populating the CodeableConcept

This section shows you how to populate each field where the code carried is a SNOMED CT Concept and where it’s not a SNOMED CT Concept. It also includes population scenarios with examples.

Field by field population guidance

SNOMED CT

Element Definition
code.coding Populate this group if a SNOMED CT Concept Id is stored for the item.
code.coding.extension
Where extension.url = http://hl7.org/fhir/StructureDefinition/coding-sctdescid		 The SNOMED CT Description Id recorded with the item. Only populated if a Description Id exists.
code.coding.extension
Where extension.url = https://fhir.hl7.org.uk/StructureDefinition/Extension-UKCore-CodingSCTDescDisplay		 The display term of the Description Id. This SHOULD be populated if a Description Id exists, but implementers SHOULD NOT populate the extension if the selected display term is lexically identical to the text in coding.display.
code.coding.system Set to http://snomed.info/sct
code.coding.code The SNOMED CT Concept Id stored for the item.
code.coding.display The text of the current preferred term of the SNOMED CT Concept Id according to the current NHS Realm Language Reference Sets.
The preferred term is the description specified for the concept in the NHS realm description subset. The preferred term for a concept may change over time. The sending system SHOULD determine the current preferred term for the concept.
code.coding.userSelected Indicates that this coding was chosen by a user directly - e.g. off a pick list of available items (codes or displays).
This should be set to true if a user selected the SNOMED CT Concept when creating/updating this item.
code.text The original text selected / manually entered by the user for the item.

Other coding

Element Definition
code.coding Populate this group if a clinical code other than SNOMED CT is stored for the item. If there are multiple codes (that is, the item has been translated multiple times) there is a group entry per code.
code.coding.extension
Where extension.url = http://hl7.org/fhir/StructureDefinition/coding-sctdescid		 Note: Do not use here if coding is not SNOMED CT.
code.coding.extension
Where extension.url = https://fhir.hl7.org.uk/StructureDefinition/Extension-UKCore-CodingSCTDescDisplay		 Note: Do not use here if coding is not SNOMED CT.
code.coding.system The identification of the code system that defines the meaning of the symbol in the code.
code.coding.code The clinical code associated with the item.
code.coding.display The longest character length variant text associated with the current preferred term for the clinical code.
code.coding.userSelected Indicates that this coding was chosen by a user directly - e.g. off a pick list of available items (codes or displays).
This should be set to true if a user selected this code when creating/updating this item.
code.text The original text selected / manually entered by the user for the item.

Sending dm+d codes

Where a supplier is using the dm+d codes which does not contain any data at the Description Id level, then we would not expect the coding-sctdescid and UKCore-CodingSCTDescDisplay extensions to be populated. Where the Description Id is available then these SHALL be included.

The example below demonstrates how a dm+d code SHOULD be sent where there is no Description Id available.

Table View

Medication.id[0]UKCore-Medication-Sn-Amoxicillin-Example
Medication.code[0].coding[0].system[0]https://dmd.nhs.uk/
Medication.code[0].coding[0].code[0]323509004
Medication.code[0].coding[0].display[0]Amoxicillin 250mg capsules
Medication.code[0].coding[0].userSelected[0]True

Tree View

Medication

XML View

<Medication xmlns="http://hl7.org/fhir">
    <id value="UKCore-Medication-Sn-Amoxicillin-Example" />
    <!--  **************Snippet start**************  -->
    <code>
        <coding>
            <system value="https://dmd.nhs.uk/" />
            <code value="323509004" />
            <display value="Amoxicillin 250mg capsules" />
            <userSelected value="true" />
        </coding>
    </code>
    <!--  **************Snippet end**************  -->
</Medication>

JSON View

{
    "resourceType": "Medication",
    "id": "UKCore-Medication-Sn-Amoxicillin-Example",
    "code": {
        "coding":  [
            {
                "system": "https://dmd.nhs.uk/",
                "code": "323509004",
                "display": "Amoxicillin 250mg capsules",
                "userSelected": true
            }
        ]
    }
}

Sending a SNOMED CT concept with its associated preferred term

When sending a SNOMED CT Concept Id with its preferred term, and the SNOMED CT Description Id is known, then the HL7 core-defined extension coding-sctdescid SHALL be used and the element sctdescid SHALL be populated. Where the SNOMED CT Description Id is not known, then the codeable concept MAY be sent without it.

In the example below, the SNOMED CT Description Id is populated with the Id of the preferred term, but there is no display term, as the Concept Id was entered by the user and the preferred term was displayed to them when it was added.

Table View

Condition.id[0]UKCore-Extension-CodingSCT-Myocardial-Example
Condition.code[0].coding[0].extension[0].url[0]http://hl7.org/fhir/StructureDefinition/coding-sctdescid
Condition.code[0].coding[0].extension[0].value[0]37436014
Condition.code[0].coding[0].system[0]http://snomed.info/sct
Condition.code[0].coding[0].code[0]22298006
Condition.code[0].coding[0].display[0]Myocardial infarction
Condition.code[0].coding[0].userSelected[0]True
Condition.subject[0].reference[0]Patient/UKCore-Patient-RichardSmith-Example

Tree View

Condition

XML View

<Condition xmlns="http://hl7.org/fhir">
    <id value="UKCore-Extension-CodingSCT-Myocardial-Example" />
    <!--  **************Snippet start**************  -->
    <code>
        <coding>
            <extension url="http://hl7.org/fhir/StructureDefinition/coding-sctdescid">
                <valueId value="37436014" />
            </extension>
            <system value="http://snomed.info/sct" />
            <code value="22298006" />
            <display value="Myocardial infarction" />
            <userSelected value="true" />
        </coding>
    </code>
    <!--  **************Snippet end**************  -->
    <subject>
        <reference value="Patient/UKCore-Patient-RichardSmith-Example" />
    </subject>
</Condition>

JSON View

{
    "resourceType": "Condition",
    "id": "UKCore-Extension-CodingSCT-Myocardial-Example",
    "code": {
        "coding":  [
            {
                "extension":  [
                    {
                        "url": "http://hl7.org/fhir/StructureDefinition/coding-sctdescid",
                        "valueId": "37436014"
                    }
                ],
                "system": "http://snomed.info/sct",
                "code": "22298006",
                "display": "Myocardial infarction",
                "userSelected": true
            }
        ]
    },
    "subject": {
        "reference": "Patient/UKCore-Patient-RichardSmith-Example"
    }
}

Sending a concept where the coding system and code is unknown

In the exceptional case that the code is not known, then the code.text element MAY be populated without the need to populate a coding element, as per the example below.

Table View

Condition.id[0]UKCore-Extension-CodingSCT-CodeUnknown-Example
Condition.code[0].text[0]Myocardial infarction
Condition.subject[0].reference[0]Patient/UKCore-Patient-RichardSmith-Example

Tree View

Condition

XML View

<Condition xmlns="http://hl7.org/fhir">
    <id value="UKCore-Extension-CodingSCT-CodeUnknown-Example" />
    <!--  **************Snippet start**************  -->
    <code>
        <text value="Myocardial infarction" />
    </code>
    <!--  **************Snippet end**************  -->
    <subject>
        <reference value="Patient/UKCore-Patient-RichardSmith-Example" />
    </subject>
</Condition>

JSON View

{
    "resourceType": "Condition",
    "id": "UKCore-Extension-CodingSCT-CodeUnknown-Example",
    "code": {
        "text": "Myocardial infarction"
    },
    "subject": {
        "reference": "Patient/UKCore-Patient-RichardSmith-Example"
    }
}

Sending a SNOMED CT Description ID that is not the preferred term

In this case, the SNOMED CT Description ID represents a term that is different from the preferred term and therefore the description display will be different from that used to populate the code.coding.display element. Therefore the extension Extension UKCore-CodingSCTDescDisplay SHALL be populated with the term corresponding to the selected SNOMED CT Description ID, as per the example below.

Table View

Condition.id[0]UKCore-Extension-CodingSCT-Heart-Example
Condition.code[0].coding[0].extension[0].url[0]https://fhir.hl7.org.uk/StructureDefinition/Extension-UKCore-CodingSCTDescDisplay
Condition.code[0].coding[0].extension[0].value[0]Heart attack
Condition.code[0].coding[0].extension[1].url[0]http://hl7.org/fhir/StructureDefinition/coding-sctdescid
Condition.code[0].coding[0].extension[1].value[0]37443015
Condition.code[0].coding[0].system[0]http://snomed.info/sct
Condition.code[0].coding[0].code[0]22298006
Condition.code[0].coding[0].display[0]Myocardial infarction
Condition.code[0].coding[0].userSelected[0]True
Condition.subject[0].reference[0]Patient/UKCore-Patient-RichardSmith-Example

Tree View

Condition

XML View

<Condition xmlns="http://hl7.org/fhir">
    <id value="UKCore-Extension-CodingSCT-Heart-Example" />
    <!--  **************Snippet start**************  -->
    <code>
        <coding>
            <extension url="https://fhir.hl7.org.uk/StructureDefinition/Extension-UKCore-CodingSCTDescDisplay">
                <valueString value="Heart attack" />
            </extension>
            <extension url="http://hl7.org/fhir/StructureDefinition/coding-sctdescid">
                <valueId value="37443015" />
            </extension>
            <system value="http://snomed.info/sct" />
            <code value="22298006" />
            <display value="Myocardial infarction" />
            <userSelected value="true" />
        </coding>
    </code>
    <!--  **************Snippet end**************  -->
    <subject>
        <reference value="Patient/UKCore-Patient-RichardSmith-Example" />
    </subject>
</Condition>

JSON View

{
    "resourceType": "Condition",
    "id": "UKCore-Extension-CodingSCT-Heart-Example",
    "code": {
        "coding":  [
            {
                "extension":  [
                    {
                        "url": "https://fhir.hl7.org.uk/StructureDefinition/Extension-UKCore-CodingSCTDescDisplay",
                        "valueString": "Heart attack"
                    },
                    {
                        "url": "http://hl7.org/fhir/StructureDefinition/coding-sctdescid",
                        "valueId": "37443015"
                    }
                ],
                "system": "http://snomed.info/sct",
                "code": "22298006",
                "display": "Myocardial infarction",
                "userSelected": true
            }
        ]
    },
    "subject": {
        "reference": "Patient/UKCore-Patient-RichardSmith-Example"
    }
}

Sending a mapped concept set

In the case where a code was entered into the clinical system using a legacy coding system and the code was mapped to a SNOMED CT Concept, the following scenario SHALL be considered.

In SNOMED CT, all Concept Ids always have more than one associated description: all have at least one fully specified name and at least one additional associated synonym. Of these, exactly one fully specified name and one synonym will be declared to be “preferred” at any point in time within a Realm Language Reference Set, but which terms are designated “preferred” can and does change over time.

Therefore, in most cases where such mappings have been created, they will have been mapped to an explicit pairing of one SNOMED CT Concept Id and one of its legitimate Description Ids. The particular Description ID selected might also correspond to the preferred term but often does not.

Exceptionally, mappings could correspond to a SNOMED CT Concept Id only and so no particular description is declared in the map. In these cases the description originally entered by the clinician in the legacy coding system SHALL be considered to be the clinically relevant text.

As per example below:

Table View

Observation.id[0]UKCore-Extension-CodingSCT-Potassium-Example
Observation.status[0]final
Observation.code[0].coding[0].extension[0].url[0]https://fhir.hl7.org.uk/StructureDefinition/Extension-UKCore-CodingSCTDescDisplay
Observation.code[0].coding[0].extension[0].value[0]Serum potassium measurement
Observation.code[0].coding[0].extension[1].url[0]http://hl7.org/fhir/StructureDefinition/coding-sctdescid
Observation.code[0].coding[0].extension[1].value[0]405941011
Observation.code[0].coding[0].system[0]http://snomed.info/sct
Observation.code[0].coding[0].code[0]1000651000000109
Observation.code[0].coding[0].display[0]Serum potassium level
Observation.code[0].coding[0].userSelected[0]True
Observation.code[0].text[0]Serum Potassium
Observation.subject[0].reference[0]Patient/UKCore-Patient-RichardSmith-Example

Tree View

Observation

XML View

<Observation xmlns="http://hl7.org/fhir">
    <id value="UKCore-Extension-CodingSCT-Potassium-Example" />
    <status value="final" />
    <!--  **************Snippet start**************  -->
    <code>
        <coding>
            <extension url="https://fhir.hl7.org.uk/StructureDefinition/Extension-UKCore-CodingSCTDescDisplay">
                <valueString value="Serum potassium measurement" />
            </extension>
            <extension url="http://hl7.org/fhir/StructureDefinition/coding-sctdescid">
                <valueId value="405941011" />
            </extension>
            <system value="http://snomed.info/sct" />
            <code value="1000651000000109" />
            <display value="Serum potassium level" />
            <userSelected value="true" />
            <!-- flags the coding originally actually selected by the user  -->
        </coding>
        <text value="Serum Potassium" />
        <!--  what the user saw on screen, from a data entry template  -->
    </code>
    <!--  **************Snippet end**************  -->
    <subject>
        <reference value="Patient/UKCore-Patient-RichardSmith-Example" />
    </subject>
</Observation>

JSON View

{
    "resourceType": "Observation",
    "id": "UKCore-Extension-CodingSCT-Potassium-Example",
    "status": "final",
    "code": {
        "coding":  [
            {
                "extension":  [
                    {
                        "url": "https://fhir.hl7.org.uk/StructureDefinition/Extension-UKCore-CodingSCTDescDisplay",
                        "valueString": "Serum potassium measurement"
                    },
                    {
                        "url": "http://hl7.org/fhir/StructureDefinition/coding-sctdescid",
                        "valueId": "405941011"
                    }
                ],
                "system": "http://snomed.info/sct",
                "code": "1000651000000109",
                "display": "Serum potassium level",
                "userSelected": true
            }
        ],
        "text": "Serum Potassium"
    },
    "subject": {
        "reference": "Patient/UKCore-Patient-RichardSmith-Example"
    }
}

Rules for populating legacy coding

Read Code

All Read Codes SHOULD be represented using a full five characters.

  • Where 4-byte codes are used these SHALL be preceded by a full-stop as in the NHS Clinical Terms superset (e.g. 4-byte code "6521" is represented as ".6521").
  • Trailing full-stops are significant and SHALL be included (e.g. "H43" is not a valid Read Code and SHALL be represented in full as "H43..").
    • Care should be taken in any environment where a Read Code may have been subjected to auto-correction because:
      • Upper/lower case is significant
      • Conversion of a sequence of three full-stops "..." to a single "…" (ASCII Hex "85" Unicode Hex "2026") special character occurs in some environments and creates invalid Read Codes.

Read Code version 2 term code

Read Codes Version 2 uses a "Term Code" to distinguish between some alternative terms associated with the same Read Code. A Term Code is represented as a two-digit string and is only unique within the context of a single Read Code.

It is now widely recognised that many of the terms associated with a Read Code are not true synonyms. This issue was partially resolved in NHS Clinical Terms Version 3 and further disambiguation has occurred in development of SNOMED CT. However, in the meantime where Term Codes are stored these SHOULD be communicated with the Read Code.

A Read Code + Term Code combination is communicated as a single seven character code. Thus the code "7001200" represents the Term Code "00" associated with the Read Code "70012".

Note: that this specification requires the term to be conveyed in the message in addition to any coded representation. Therefore, safe communication is not dependent on use of the Term Code in all systems. Therefore, a sending system that does not support Term Codes for a particular item of information SHOULD NOT send a Term Code. Similarly a receiving system that does not support Term Code storage MAY ignore the Term Code when constructing a record entry. However, where a sending system stores the Term Code this SHOULD be included in the message and where a receiving system stores the Term Code this SHOULD be retrieved from the message.

NHS Clinical Terms Version 3 – Term Id

In NHS Clinical Terms Version 3 the Term Id is a five character string that uniquely identifies an associated term (or set of two or three terms of alternative lengths). Although it is globally unique it says nothing about the associated concept and thus SHALL be combined with the Read Code. There are no plans to use the Term Id in NHS Clinical Terms Version 3 and thus inclusion of Term Id is not permitted.

Example of Condition.code usage for legacy coding:

Table View

Condition.id[0]UKCore-Extension-CodingSCT-MoleOfSkin-Example
Condition.code[0].coding[0].system[0]http://read.info/ctv3
Condition.code[0].coding[0].code[0]X78Uv
Condition.code[0].coding[0].display[0]Benign melanocytic naevus skin
Condition.code[0].coding[1].extension[0].url[0]https://fhir.hl7.org.uk/StructureDefinition/Extension-UKCore-CodingSCTDescDisplay
Condition.code[0].coding[1].extension[0].value[0]Mole of skin
Condition.code[0].coding[1].extension[1].url[0]http://hl7.org/fhir/StructureDefinition/coding-sctdescid
Condition.code[0].coding[1].extension[1].value[0]1787065011
Condition.code[0].coding[1].system[0]http://snomed.info/sct
Condition.code[0].coding[1].code[0]400010006
Condition.code[0].coding[1].display[0]Melanocytic naevus of skin
Condition.code[0].text[0]Moles
Condition.subject[0].reference[0]Patient/UKCore-Patient-RichardSmith-Example

Tree View

Condition

XML View

<Condition xmlns="http://hl7.org/fhir">
    <id value="UKCore-Extension-CodingSCT-MoleOfSkin-Example" />
    <!--  **************Snippet start**************  -->
    <code>
        <coding>
            <system value="http://read.info/ctv3" />
            <code value="X78Uv" />
            <!--  no term code, so CTV3 PT is implied?  -->
            <display value="Benign melanocytic naevus skin" />
            <!--  text of V3 PT  -->
        </coding>
        <coding>
            <extension url="https://fhir.hl7.org.uk/StructureDefinition/Extension-UKCore-CodingSCTDescDisplay">
                <valueString value="Mole of skin" />
                <!--  text for id = 1787065011  -->
            </extension>
            <extension url="http://hl7.org/fhir/StructureDefinition/coding-sctdescid">
                <valueId value="1787065011" />
                <!--  not the SNOMED PT  -->
            </extension>
            <system value="http://snomed.info/sct" />
            <code value="400010006" />
            <!--  SNOMED conceptId  -->
            <display value="Melanocytic naevus of skin" />
            <!--  text of SNOMED PT  -->
        </coding>
        <text value="Moles" />
        <!--  what user saw on screen, from data entry template  -->
    </code>
    <!--  **************Snippet end**************  -->
    <subject>
        <reference value="Patient/UKCore-Patient-RichardSmith-Example" />
    </subject>
</Condition>

JSON View

{
    "resourceType": "Condition",
    "id": "UKCore-Extension-CodingSCT-MoleOfSkin-Example",
    "code": {
        "coding":  [
            {
                "system": "http://read.info/ctv3",
                "code": "X78Uv",
                "display": "Benign melanocytic naevus skin"
            },
            {
                "extension":  [
                    {
                        "url": "https://fhir.hl7.org.uk/StructureDefinition/Extension-UKCore-CodingSCTDescDisplay",
                        "valueString": "Mole of skin"
                    },
                    {
                        "url": "http://hl7.org/fhir/StructureDefinition/coding-sctdescid",
                        "valueId": "1787065011"
                    }
                ],
                "system": "http://snomed.info/sct",
                "code": "400010006",
                "display": "Melanocytic naevus of skin"
            }
        ],
        "text": "Moles"
    },
    "subject": {
        "reference": "Patient/UKCore-Patient-RichardSmith-Example"
    }
}

Sending a Description Id not in the UK Edition

Sending a Description Id not in the UK Edition, but for a concept id that is in the UK Edition

Includes the case where the Description Id is locally declared to be the preferred term, as per example below.

Table View

Observation.id[0]UKCore-Extension-CodingSCT-Weight-Example
Observation.status[0]final
Observation.code[0].coding[0].extension[0].url[0]https://fhir.hl7.org.uk/StructureDefinition/Extension-UKCore-CodingSCTDescDisplay
Observation.code[0].coding[0].extension[0].value[0]Ideal weight
Observation.code[0].coding[0].extension[1].url[0]http://hl7.org/fhir/StructureDefinition/coding-sctdescid
Observation.code[0].coding[0].extension[1].value[0]787121000006116
Observation.code[0].coding[0].system[0]http://snomed.info/sct
Observation.code[0].coding[0].code[0]170804003
Observation.code[0].coding[0].display[0]Ideal body weight
Observation.code[0].coding[0].userSelected[0]True
Observation.subject[0].reference[0]Patient/UKCore-Patient-RichardSmith-Example

Tree View

Observation

XML View

<Observation xmlns="http://hl7.org/fhir">
    <id value="UKCore-Extension-CodingSCT-Weight-Example" />
    <status value="final" />
    <!--  **************Snippet start**************  -->
    <code>
        <coding>
            <extension url="https://fhir.hl7.org.uk/StructureDefinition/Extension-UKCore-CodingSCTDescDisplay">
                <valueString value="Ideal weight" />
            </extension>
            <extension url="http://hl7.org/fhir/StructureDefinition/coding-sctdescid">
                <valueId value="787121000006116" />
                <!--  descriptionId from a GP system namespace  -->
            </extension>
            <system value="http://snomed.info/sct" />
            <code value="170804003" />
            <!--  conceptId from SNOMED International CORE  -->
            <display value="Ideal body weight" />
            <userSelected value="true" />
        </coding>
    </code>
    <!--  **************Snippet end**************  -->
    <subject>
        <reference value="Patient/UKCore-Patient-RichardSmith-Example" />
    </subject>
</Observation>

JSON View

{
    "resourceType": "Observation",
    "id": "UKCore-Extension-CodingSCT-Weight-Example",
    "status": "final",
    "code": {
        "coding":  [
            {
                "extension":  [
                    {
                        "url": "https://fhir.hl7.org.uk/StructureDefinition/Extension-UKCore-CodingSCTDescDisplay",
                        "valueString": "Ideal weight"
                    },
                    {
                        "url": "http://hl7.org/fhir/StructureDefinition/coding-sctdescid",
                        "valueId": "787121000006116"
                    }
                ],
                "system": "http://snomed.info/sct",
                "code": "170804003",
                "display": "Ideal body weight",
                "userSelected": true
            }
        ]
    },
    "subject": {
        "reference": "Patient/UKCore-Patient-RichardSmith-Example"
    }
}

Sending a Description Id and concept id where neither is in the UK Edition

Table View

Observation.id[0]UKCore-Extension-CodingSCT-IllicitDrugs-Example
Observation.status[0]final
Observation.code[0].coding[0].extension[0].url[0]https://fhir.hl7.org.uk/StructureDefinition/Extension-UKCore-CodingSCTDescDisplay
Observation.code[0].coding[0].extension[0].value[0]Illicit medication use unknown
Observation.code[0].coding[0].extension[1].url[0]http://hl7.org/fhir/StructureDefinition/coding-sctdescid
Observation.code[0].coding[0].extension[1].value[0]3449865011
Observation.code[0].coding[0].system[0]http://snomed.info/sct
Observation.code[0].coding[0].code[0]702771005
Observation.code[0].coding[0].display[0]Illicit drug use unknown
Observation.code[0].coding[0].userSelected[0]True
Observation.code[0].text[0]Not known whether uses illicit drugs
Observation.subject[0].reference[0]Patient/UKCore-Patient-RichardSmith-Example

Tree View

Observation

XML View

<Observation xmlns="http://hl7.org/fhir">
    <id value="UKCore-Extension-CodingSCT-IllicitDrugs-Example" />
    <status value="final" />
    <!--  **************Snippet start**************  -->
    <code>
        <coding>
            <extension url="https://fhir.hl7.org.uk/StructureDefinition/Extension-UKCore-CodingSCTDescDisplay">
                <valueString value="Illicit medication use unknown" />
            </extension>
            <extension url="http://hl7.org/fhir/StructureDefinition/coding-sctdescid">
                <valueId value="3449865011" />
            </extension>
            <system value="http://snomed.info/sct" />
            <code value="702771005" />
            <display value="Illicit drug use unknown" />
            <userSelected value="true" />
        </coding>
        <text value="Not known whether uses illicit drugs" />
        <!--  what the user saw on screen, from a data entry template  -->
    </code>
    <!--  **************Snippet end**************  -->
    <subject>
        <reference value="Patient/UKCore-Patient-RichardSmith-Example" />
    </subject>
</Observation>

JSON View

{
    "resourceType": "Observation",
    "id": "UKCore-Extension-CodingSCT-IllicitDrugs-Example",
    "status": "final",
    "code": {
        "coding":  [
            {
                "extension":  [
                    {
                        "url": "https://fhir.hl7.org.uk/StructureDefinition/Extension-UKCore-CodingSCTDescDisplay",
                        "valueString": "Illicit medication use unknown"
                    },
                    {
                        "url": "http://hl7.org/fhir/StructureDefinition/coding-sctdescid",
                        "valueId": "3449865011"
                    }
                ],
                "system": "http://snomed.info/sct",
                "code": "702771005",
                "display": "Illicit drug use unknown",
                "userSelected": true
            }
        ],
        "text": "Not known whether uses illicit drugs"
    },
    "subject": {
        "reference": "Patient/UKCore-Patient-RichardSmith-Example"
    }
}

Clinical codes

Storage

When storing the item, the receiving system MAY choose to store any or all of the clinical codes associated with the item.

However, where the system supports SNOMED CT codes it SHALL store any SNOMED CT codes associated with the item.

Where the receiving system does not understand any of the supplied coding.system which a coding has been associated with the item (or no clinical codes were supplied), it MAY choose to record the item under a degraded code. The appropriate SNOMED CT degrade code SHOULD be used within the system to store the code.

The following concepts are available in SNOMED CT to represent degraded items and can be used when populating FHIR resources.
Degraded Drug Allergies 196461000000101 - Transfer-degraded drug allergy
Degraded Non-Drug Allergies 196471000000108 - Transfer-degraded non-drug allergy
Degraded Medications 196421000000109 - Transfer-degraded medication entry
Degraded Plan 196451000000104 - Transfer-degraded plan
Degraded Referral 196431000000106 - Transfer-degraded referral
Degraded Request 196441000000102 - Transfer-degraded request
Other degrade 196411000000103 - Transfer-degraded record entry

Where an item that is being degraded is contained within a resource that infers a particular type of degrade then the appropriate code SHALL be used e.g. a code in a FHIR medication resource SHALL use the ‘Transfer-degraded medication entry’ code.

Clinical systems SHALL NOT attempt to infer a particular type of degrade code where there is no clear indication that a specific type of data has been degraded. In these scenarios the ‘Transfer-degraded record entry’ code SHALL be used.

Display

When displaying the item to end users, it is the choice of the receiving system to design their system and user experience in a safe manner that best suits their users.

Propagation

When propagating coded data to another system, the system which received the item MAY choose which clinical codes to include when sending the item.

If a receiving system receives a SNOMED CT code that it does not understand it SHOULD store this code and propagate it onwards if the data is exported. If systems decide to do this, a consideration that might be useful is what would happen if the data item is changed/edited.

Original term text

Storage

When processing an item, the receiving system SHALL always store the original term text of the item. That is, the text chosen/manually entered by the clinician/user to describe the item they are recording. Failure to do this could result in the intended meaning of the item being altered.

The original term text will be available in one of the following fields in order of descending priority:

  1. text
  2. coding.extension.valueString in Extension UKCore-CodingSCTDescDisplay where coding.userSelected = TRUE (or is unpopulated, and only one coding element is present)
  3. coding.display where coding.userSelected = TRUE (or is unpopulated, and only one coding element is present)

Where the receiving system can derive the original term text from the clinical code and the derived text is lexically identical to the original term text, then the receiving system is not required to store the text separately.

However, where the system supports SNOMED CT codes it SHALL store any SNOMED CT codes associated with the item where the coding.userSelected is set to ‘TRUE’ and propagate these onward in any future export of the data. As noted previously, some SNOMED CT codes received may be from a release or extension of SNOMED CT not available on the receiving system.

Display

When displaying an item to end users, the receiving system SHALL always display the original term text of the item.

Propagation

When propagating an item to another system, the receiving system SHALL always include the original term text of the item.

Sending a local language translation

Where a supplier wants to send the local language translation with a description or text field, they can use the HL7 Core-defined Extension translation.

The example below demonstrates how a translation SHOULD be sent.

Table View

Condition.id[0]UKCore-Extension-Translation-Example
Condition.code[0].coding[0].system[0]http://snomed.info/sct
Condition.code[0].coding[0].code[0]22298006
Condition.code[0].coding[0].display[0]Myocardial infarction
Condition.code[0].coding[0].display[0].extension[0].extension[0].url[0]lang
Condition.code[0].coding[0].display[0].extension[0].extension[0].value[0]fr
Condition.code[0].coding[0].display[0].extension[0].extension[1].url[0]content
Condition.code[0].coding[0].display[0].extension[0].extension[1].value[0]Infarctus du myocarde
Condition.code[0].coding[0].display[0].extension[0].url[0]http://hl7.org/fhir/StructureDefinition/translation
Condition.subject[0].reference[0]Patient/UKCore-Patient-RichardSmith-Example

Tree View

Condition

XML View

<Condition xmlns="http://hl7.org/fhir">
    <id value="UKCore-Extension-Translation-Example" />
    <!--  **************Snippet start**************  -->
    <code>
        <coding>
            <system value="http://snomed.info/sct" />
            <code value="22298006" />
            <display value="Myocardial infarction">
                <extension url="http://hl7.org/fhir/StructureDefinition/translation">
                    <extension url="lang">
                        <valueCode value="fr" />
                    </extension>
                    <extension url="content">
                        <valueString value="Infarctus du myocarde" />
                    </extension>
                </extension>
            </display>
        </coding>
    </code>
    <!--  **************Snippet end**************  -->
    <subject>
        <reference value="Patient/UKCore-Patient-RichardSmith-Example" />
    </subject>
</Condition>

JSON View

{
    "resourceType": "Condition",
    "id": "UKCore-Extension-Translation-Example",
    "code": {
        "coding":  [
            {
                "system": "http://snomed.info/sct",
                "code": "22298006",
                "display": "Myocardial infarction",
                "_display": {
                    "extension":  [
                        {
                            "url": "http://hl7.org/fhir/StructureDefinition/translation",
                            "extension":  [
                                {
                                    "url": "lang",
                                    "valueCode": "fr"
                                },
                                {
                                    "url": "content",
                                    "valueString": "Infarctus du myocarde"
                                }
                            ]
                        }
                    ]
                }
            }
        ]
    },
    "subject": {
        "reference": "Patient/UKCore-Patient-RichardSmith-Example"
    }
}
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