SNOMED CT to Classifications Maps

SNOMED CT UK Edition, OPCS-4 and ICD-10

The OPCS-4 and ICD-10 classifications are used across the UK for submissions of aggregated information to national database collections for statistical analyses. They are a vital component of national datasets such as: Hospital Episode statistics (HES) in England, Patient Episode Data for Wales (PEDW), Scottish Morbidity Records (SMR), Cancer Registries, performance indicators and commissioning currencies - National Tariff payment system.

All three NHS Information Standards (SNOMED CT, OPCS-4 and ICD-10) are a national requirement, serve different purposes and are complimentary.

SNOMED CT is the vocabulary for use in an Electronic Patient Record (EPR). It is focused on what clinicians want to record at the point of patient care for the direct management of the patient. It includes, but is not limited to diagnoses, procedures, symptoms, family history, allergies, assessment tools, observations and medication (dm+d).

OPCS-4 and ICD-10 are clinical classifications which are used after the event in Patient Administration Systems (PAS) to report/summarise a Consultant Episode of patient care (for the Admitted Patient Care Commissioning Dataset). They are applied in accordance with classifications business rules and conventions and focus on what we want to ‘count’ for statistical and epidemiological analyses. Because entities in the classifications have a single parent they are mutually exclusive to ensure there is no ‘double counting’.

presentation providing an overview of SNOMED CT for clinical coders is available in the Resource Library.

Classification Maps

The SNOMED CT UK Edition consists of the International Edition, plus the UK Clinical Extension and UK Drug Extension which contains content for use in the UK only. The UK Edition also provides maps from SNOMED CT to the OPCS-4 and ICD-10 classifications.

The UK maps are a link from SNOMED CT to OPCS-4 and ICD-10. Compiled to reflect the national clinical coding standards and aid the application of the three dimensions of coding accuracy (individual codes, totality of codes, and sequencing of codes) they support the derivation of classification codes directly from the SNOMED CT concepts which have been recorded by the clinician in the EPR. They are incorporated in software to present to the coding expert the OPCS-4 and ICD-10 code or codes which have been attached to a SNOMED CT concept.

There are four different types of maps in order to represent the multiplicity of circumstances encountered in a medical record.

Map Type 1

Links a single SNOMED CT concept to a single classification code to represent the clinical meaning of the concept. 

Map Type 2

Links a single SNOMED CT concept to a combination of classification codes which collectively represents the meaning of the SNOMED CT concept. These simple maps may be generated automatically within systems allowing the coding expert to devote time to the resolution of more complex maps.

Map Type 3

Links a single SNOMED CT concept to a choice of classification codes (default and alternative targets). Resolution of the choices involves a coding expert using the clinical detail found within the medical record, applying the rules, conventions and standards of the classifications and manually selecting the final classification code or codes from a list of alternative targets.

Map Type 4

Links a single SNOMED CT concept to a choice of classifications maps. Each choice of map may contain a single, combination or choice of target codes. Final selection will be informed by clinical detail within the medical record and application of classification expertise by the coder.

The maps:

  • are updated and published as part of the SNOMED CT UK Edition release.
  • are compiled to reflect national clinical coding standards and the three dimensions of coding accuracy: individual codes, totality of codes and sequencing of codes.
  • are available for download from TRUD. To access content via TRUD, you will need to register and complete the required license agreement.

The associated release information can be found in the SNOMED CT UK Clinical Extension Release Documentation area in:

  • Release Notes: SNOMED CT to ICD-10 and OPCS-4 Classification Maps
  • Release Documents: SNOMED CT to ICD-10 and OPCS-4 Map Table Technical Specification and Implementation Guidance (UK Edition)

The NHS Digital SNOMED CT Browser and Classification Maps

The NHS Digital SNOMED CT Browser allows users to browse and search the SNOMED CT UK Edition content, including the classification maps, and is available to anyone for reference purposes.

See the UK Classifications Maps in the NHS Digital SNOMED CT Browser document for information on using the Browser maps.

Learn more about SNOMED CT

If you want to find out more, you may find our SNOMED CT Education & eLearning resources useful.

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