Classification 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. 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 to report/summarise an episode of 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 on how SNOMED CT and the classifications can work together is available in the Resource Library.

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Classification Maps

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

  • Simple map (map type 1): Links a single SNOMED CT concept to a single classification code to represent the clinical meaning of the concept.
  • Complex map (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.
  • Complex map (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.

The maps are compiled to reflect national clinical coding standards and the three dimensions of coding accuracy: individual codes, totality of codes and sequencing of codes.

The maps are updated twice a year and are published as part of the SNOMED CT UK Edition releases on 1 April and 1 October each year.

The maps and associated documentation are available for download from TRUD. To access content via TRUD, you will need to register and complete the required license agreement.

The classification maps can also be viewed using NHS Digital SNOMED CT Browser (see below for further information).


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The NHS Digital SNOMED CT Browser and the Classification Maps

The NHS Digital SNOMED CT Browser allows users to browse and search the SNOMED CT UK Edition and is available to anyone for reference purposes. The SNOMED CT UK Edition is released twice per year and consists of the International Edition plus the UK-specific content provided within the UK Clinical Extension and UK Drug Extension and which is for use in the UK only. The UK edition also provides maps from SNOMED CT to the OPCS-4 and ICD-10 classifications.

Access the NHS Digital SNOMED CT Browser

Using the UK classification maps in the NHS Digital SNOMED CT Browser.

Further Information

Information about mapping from SNOMED CT to ICD-10 in the UK can also be found in the NHS Digital poster from the WHO - Family of International Classification Network Annual Meeting 2017


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Last modified by Mandy Hudson 11 months ago