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About Clinical Classifications and Coding


Clinical Classifications are the standardised groupings of information that allow specialist Clinical Coders to translate the medical terminology used in healthcare settings that describe a patient's complaint, problem, diagnosis, treatment, or other reason for seeking medical attention into codes that can be easily tabulated, aggregated, and sorted for statistical analysis in an efficient and meaningful manner.

Classifications data are just one of many information groupings that are collected within the NHS, but as the classifications deal directly with the translation of complex specialist terminology regarding diagnoses and procedures, dedicated training, audit and verification processes are fundamental to maintaining the accuracy and completeness of classifications data.

Each Local Health Board and Trust within NHS Wales maintains a dedicated Clinical Coding department for the coding of Diagnoses and Procedures as part of the Admitted Patient Care (APC) Dataset. 

The DHCW Clinical Classifications Team provides a central point of contact for communications, training and audit, as well as maintaining and updating Welsh Standards and Guidance for data quality and consistency. We also provide a point of contact between NHS organisations in Wales and national and international standards organisations. The two classifications currently in use in the UK are ICD-10 5th Edition and OPCS-4.


The International Statistical Classification of Diseases and related health problems, tenth version (ICD-10), 5th Edition is used to record morbid conditions affecting a patient. It is produced and maintained by the World Health Organisation (WHO), and used internationally. 


ICD-10 book






The Office of Population, Census and Surveys Classification of interventions and procedures version 4 (OPCS-4) is used to record interventions and procedures carried out on a patient during their time in hospital. It is produced and maintained by NHS England, and used within the UK.


OPCS books








Both ICD-10 5th Edition and OPCS-4 are clinical classifications, a system of categories to which entities are assigned according to established criteria. Their purpose is to translate diagnostic and operative information into alphanumeric code, which permits easy storage, retrieval and analysis of the data. They are designed to aggregate complex medical concepts into a form for statistical analysis. Unlike the Clinical Terminology in use in healthcare settings in the UK, SNOMED CT, they are NOT designed to support direct patient care or the communication of clinical information between clinical staff.