This website places cookies on your device to help us improve our service to you. To find out more about the cookies, see our Privacy and Cookies notice
ISD Scotland better information, better decisions, better health

Coding and Terminology Systems

Terminology Services and Clinical Coding

NHS National Services Scotland ISD Scotland & NHS National Services Scotland

Coding & Terminology Systems

What is Terminology?

Clinical terminology is a structured collection of descriptive terms which are used in clinical practice at the point of care. Terminology includes items such as treatments, diagnoses, administrative terms, social and environmental factors.

What is coding?

Coding is the translation of clinical terminology into an (alpha) numeric code to make it easier to analyse data for management and epidemiological purposes. By supporting the process of collecting better quality information through accurate coding we contribute to the decisions that inform health care policy which ultimately leads to improvements in patient health.

Clinical and health related data are collected on various national patient based datasets (e.g. Scottish Morbidity records, Scottish Cancer Registry). To ensure data is recorded consistently and accurately, nationally agreed coding systems are used.

These are:

  • The International Classification of Diseases, Tenth Revision (ICD-10) for diagnoses
  • Office of Population Censuses and Surveys, Fourth Revision (OPCS-4) for procedures and interventions
  • Read codes for primary care
  • Clinical Imaging Procedure codes

SNOMED-CT will eventually become the terminology of choice covering both primary and secondary care. It will encompass all coding systems mentioned above, allowing NHS Scotland to progress towards an electronic patient record.


The International Statistical Classification of Diseases and Related Health Problems (ICD) is a detailed index of diseases and injuries that is developed and released by the World Health Organisation (WHO). Details of a diagnosis are recorded by a clinician in the patient's medical notes. These are translated into ICD-10 codes by a clinical coder. This allows consistency when selecting and comparing conditions. It is possible to select and compare conditions consistently, not only in Scotland but also across the world wherever ICD-10 is used. The information can be used for epidemiological purposes, health service planning and clinical audit at both a national and local level.

ICD is revised periodically and is currently in its tenth edition. ICD-10 was developed in 1992 to track morbidity statistics and Scotland adopted its use in 1996. Since its launch there have been 2 major updates and minor annual updates which are published by WHO. ICD-10 Version 5 (5th edition 2016) is the current standard used in NHS Scotland and was implemented for the recording of patient morbidities detailed in hospital discharges on and after April 1st 2016.

Help and information on ICD-10 is available from the Terminology Advisory Service helpdesk on 0131 275 7283 or via email.


The Office of Population Censuses and Surveys' Classification of Surgical Operations version-4 (OPCS-4) was first issued in September 1987 to record operations and procedures carried out in the acute sector although coding of surgical procedures had been ongoing since 1944. It is now in its sixth revision with the latest release, OPCS-4.7, implemented in April 2014 and was expanded to include interventions. In Scotland OPCS codes are used in SMR returns to record operations, procedures and interventions. The NHS Digital Clinical Classifications Services maintain and develop OPCS on behalf of the UK. OPCS-4.8 is the current standard used in NHS Scotland and was implemented for the recording of patient interventions detailed in hospital discharges on and after April 1st 2017.

Additions or enhancements to the OPCS codes can be requested via NHS Digital via their OPCS-4 Requests Portal.

Help and information on OPCS Codes is available from the Terminology Advisory Service helpdesk on 0131 275 7283 or via email.


Read codes originated as a thesaurus designed specifically to enable general practitioners to code and record all relevant information arising from a patient encounter. Read codes have become widely used in general practice and primary care. The Read codes enable a summary of the medical record to be coded and stored in a computer system and contain mapping fields/tables which can provide mapping to ICD-10 (International Statistical Classification of Diseases and Health Related Problems, Tenth Revision) and OPCS-4 (Office of Population Censuses and Surveys, Fourth Revision) codes. We would recommend that you consult our advisory service if you require advice on these mappings.

The de facto standard for Scotland is 5-byte Version 2 Read Codes (Scottish). Scottish users downloading the browser from the TRUD download site should choose the option offering the Scottish variation.

Please note that Read coding is being retired and will eventually be replaced by SNOMED CT. The last ever update to Read V2 was the April 2016 release. Please see our home page news section for  further details.

Help and information on Read Codes is available from the Terminology Advisory Service helpdesk on 0131 275 7283 or via email.


The Systematised Nomenclature of Medicine - Clinical Terms, SNOMED-CT, is a result of a collaboration between the College of American Pathologists and the NHS in the UK. In January 2002 SNOMED-CT® was created by the merger, expansion and restructuring of SNOMED RT ® (Reference Terminology) and the UK NHS Clinical Terms Version 3 (also known as the Read Codes). The historical strength of SNOMED RT was its terminologies for speciality medicine, while the strength of Clinical Terms Version 3 was its terminologies for General Practice. By combining these two systems, SNOMED-CT is the most comprehensive clinical vocabulary available covering most aspects of clinical medicine with over 414,000 concepts covering diseases, clinical findings and procedures. It also allows a consistent way to index, store, retrieve and aggregate clinical data across specialities and sites of care. It also helps structure and computerise the medical record, reducing the variability in the way data is captured, encoded and used for clinical care of patients and research. SNOMED-CT created a common clinical language that is a necessary element of a health care information infrastructure.

SNOMED-CT content is updated twice a year in the UK in April and October and the Terminology Service co-ordinate code requests from users in Scotland.

Help and information on SNOMED-CT is available from the Terminology Advisory Service helpdesk on 0131 275 7283 or via email.

For more information on SNOMED CT please visit our SNOMED CT Resources page

SNOMED CT itself can be downloaded from the NHS Digital electronic distribution site - known as TRUD (registration is required and subscribers will need to sign up to the terms and conditions of the licence before downloading).. TRUD also contains additional training material. Before downloading and using SNOMED CT you may find it helpful to read the SNOMED CT: where to start document which explains some basics about SNOMED CT - its structure, how to download and information on licensing. Please note - TRUD should not be used in Scotland for downloading classification files (OPCS and ICD-10). Scottish versions of these files are available from NSS ISD.

Clinical Imaging Procedures

The National Interim Clinical Imaging Procedure Codes are code and term descriptions of Clinical Imaging Procedures in electronic systems in the NHS. They can be downloaded by registering on the NHS TRUD download site.

Help and information on Clinical Imaging Procedure Codes is available from the Terminology Advisory Service helpdesk on 0131 275 7283 or via email.

© ISD Scotland 2010
Information Services Division,
NHS National Services Scotland,
Gyle Square,
1 South Gyle Crescent,
Edinburgh EH12 9EB,
Tel: 0131 275 7050  
Contact Us

About Information Services Division | Contact Us | Accessibility | Complaints
Copyright | Terms and Conditions | Privacy | Freedom of Information

ISD is a division of NHS NSS
Working at the very heart of the health service, NSS delivers services critical to frontline patient care and in support of the efficient and effective operation of NHS Scotland. Visit the NSS Website for more information