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Clinical terminologies

Brief guidance on how clinical terminologies are expected to be used within GP Connect

Terminology and classifications

NHS Digital Information Standards({:target=”_blank”} are responsible for the UK management of SNOMED CT, Read Codes and other healthcare terminology products.

They also maintain the NHS Dictionary of Medicines and Devices (dm+d) in partnership with the NHS Business Service Authority.

SNOMED CT, READ2 & CTV3 code usage

GP Connect systems are expected to handle coded data as follows:

  • data originally entered into a system using the preferred system (that is, SNOMED CT)
    • SHALL be returned as SNOMED CT. The SNOMED CT DescriptionID should be included in addition to the ConceptID where available. The DescriptionID can convey a different meaning to the ConceptID due to the difference in the specific wording used for the two codes.
    • if no suitable code exists in the value set (that is, if only text is available, then just text MAY be used)
  • data originally entered into a system using an alternate coding system (for example, READ2 or CTV3)
    • SHALL be returned in the code system it was originally entered in (for example, READ2 or CTV3) AND
    • SHALL also be returned as a preferred code (that is, SNOMED CT) if a valid mapping/alternate code exists (for example, there is an NHS Digital assured READ2 or CTV3 to SNOMED CT mapping in place)

Assured mappings

Assured mappings can be found in the NHS Data Migration download.

Case sensitivity of terminologies

FHIR terminologies

Throughout this specification, coded values are always treated as a pair composed of ‘system’ and ‘code’, where the system is a URL that identifies the code system that defines the codes.


  • system values are always case sensitive
  • different code systems make their own rules as to whether the codes they define are case sensitive or not
  • all the codes defined by FHIR itself are case sensitive and SHALL be used in the provided case (usually, but not always, lowercase)

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