SNOMED CT to Classifications Maps

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

OPCS-4, ICD-10 and SNOMED CT are all NHS Information Standards; they are complementary, but serve different purposes.

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:

In a secondary care setting, OPCS-4 and ICD-10  are used to enter retrospective data into Patient Administration Systems (PAS) to report/summarise a Consultant Episode of patient date (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 avoid 'double counting'.

SNOMED CT is the vocabulary for use in an Electronic Patient Record (EPR) in both primary and secondary care settings. It focuses 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).

The SNOMED CT UK Edition consists of the International Edition, the UK Clinical Extension and the UK Drug Extension. Maps from SNOMED CT to OPCS-4 and ICD-10 are also published as part of the UK Clinical Extension release and are available to download from TRUD

Classification Maps

The UK maps provide a one directional link from SNOMED CT to OPCS-4 and ICD-10. 

They are 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 SNOMED CT concepts recorded by the clinician in the EPR. They are incorporated in software to present the OPCS-4 and ICD-10 code(s) attached to a SNOMED CT concept, for validation by the clinical coding expert.

Four different types of map are provided to accommodate the different circumstances that may influence ICD-10/OPCS-4 code assignment. 

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

Links a single SNOMED CT concept to a combination of classification codes which collectively represents the meaning of the SNOMED CT concept.

Map Type 1 and 2 may be generated automatically within systems, allowing the coding expert to devote time to the validation of more complex maps.

Links a single SNOMED CT concept to a choice of classification codes (default and alternative targets). Validation involves a coding expert using the additional 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.

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 additional detail within the medical record and application of classification expertise by the coder.

The NHS Digital SNOMED CT Browser and Classifications 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 Classification Maps in the NHS Digital SNOMED CT Browser document for information on using the Browser maps.

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