Facilitator Handbook 2005 - PRIMIS

Clinical Coding
PRIMIS Facilitator Handbook
Clinical Coding
Background
General practice systems use ‘clinical coding’ to store data. To record data, the user enters a
medical term or concept. The computer system then presents a set of ‘terms’ or ‘rubrics’,
together with ‘codes’. Assisted by the rubric, a choice is made and the data item is thereby
recorded. An important part of setting recording guidelines is to ensure that appropriate codes
are assigned for the items in the data set and that these codes are used for entering data in
the patient’s record at the appropriate stage in the cycle of care.
In the early 1980s, Dr James Read developed a coding system for general practice for the
purpose of maintaining a computerised patient record. It allowed for increased efficiency and
improved preventative procedures. This coding system became known as the ‘Read Code’ and
remains as the accepted standard for British general practice. The coding system copyright
was purchased by the Secretary of State for Health in 1990 and the Read Code became
Crown Copyright. It has been subsequently developed in later versions to include terminology
content appropriate for a wider range of health care specialities and professional groups. All
versions of the Read Code are maintained and developed by NHS Connecting for Health.
There are three versions of the Read Code currently in use as shown in the box below:
The current three versions of Read Code in general practice
• GP 4 byte set (referred to as Version 0)
• GP 5 byte set (referred to as Version 2)
• Clinical Terms Version 3 (referred to as CTV3)
The GP 4 byte set was developed for use in GP systems and the codes are four characters
long, allowing four levels of detail. The GP 5 byte set extended the codes to five characters -
and thus a fifth level of detail - and included cross reference to the International Classification
of Diseases tenth revision ICD-10. Clinical Terms version 3 (CTV3) incorporates
comprehensive codes for the acute sector, as well as general practice, allowing for storage,
retrieval, cross-mapping and analysis of patient information. The mostly widely used set within
GP clinical systems at present is the GP 5 byte set.
The important point to be aware of is the ‘hierarchical’ nature of Read codes, as demonstrated
in the example shown below. As the diagnosis becomes more specific, so the appropriate
Read code carries more significant characters to reflect the greater level of detail. The coding
scheme is a structured collection of ‘terms’ with each clinical entity, known as a concept, being
represented by a preferred term. Each concept has a unique alphanumeric code, known as the
Read code.
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