Read code: Difference between revisions

Revision as of 15:14, 16 November 2016

Revision as of 15:15, 16 November 2016

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Since its origins in the 1980s,<ref>Benson, Tim. "The history of the Read codes: the inaugural James Read Memorial Lecture 2011." ''Informatics in primary care'' 19.3 (2011): 173-182. http://www.ingentaconnect.com/content/bcs/ipc/2011/00000019/00000003/art00008</ref> the system has evolved through three major technical design changes and significantly expanded its content.

===READ version 1 (4-Bytebyte READ)===

The first version was developed in the early 1980s by Dr James Read, a Loughborough general medical practitioner.<ref name="BCS">{{cite web |vauthors=Bentley T, Price C, Brown P |title=Structural and lexical features of successive versions of the Read Codes |url=http://www.phcsg.org/main/pastconf/camb96/readcode.htm |work=The Proceedings of the 1996 Annual Conference of The Primary Health Care Specialist Group of the [[British Computer Society]] |date=13–15 September 1996 |accessdate=2010-04-17}}</ref> The scheme was structured similarly to [[International Statistical Classification of Diseases and Related Health Problems|ICD-9]]:

* each code comprised four consecutive characters: first character 0-9, A-Z (excepting I and O), remaining three characters 0-9, A-Z/a-z (excepting i,I,o and O) plus up to three trailing period '.' characters

* the relative position of one code to another was represented through the code itself: [J...] is the common ancestor of all other codes with 'J' as the first character, and [J1..] in turn the common ancestor of all codes beginning 'J1'.

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Because of its four character code structure, READ Codes version 1 was more commonly known as 4-Byte READ. The first release was in April 1986; the final official release of 4-Byte READ occurred in April 2009.

===READ version 2 (5-Bytebyte READ)===

4-Byte READ could only encode a monoaxial hierarchy with a maximum of 4 hierarchical levels. The operational NHS requirement to provide a direct crossmap to both [[ICD|ICD-9-CM]] and [[OPCS|OPCS-4]] implied an additional hierarchical level was required. Accordingly, a new scheme was devised with exactly the same technical properties as 4-Byte READ except that the code structure was extended to 5-Bytes. This became known as READ2, or 5-Byte READ. The first release of 5-Byte READ occurred sometime prior to January 1991. The October 2010 release contained 82,967 discrete 5-byte codes (although the actual number of discrete clinical concepts that may be represented is estimated to be slightly lower - 82,593 - because of duplicate entries).

A later extension of READ version 2 product family was the co-publication of a drug and appliance dictionary. This follows the same technical structure (5-character alphanumeric codes with first character lower case alpha organised in a monohierarchy). Released every four weeks, the October 2010 release contained 52,316 codes.

A popular misconception is that all 4-Byte codes are also present in 5-Byte, where they will also carry the same meaning. Whilst in the majority of cases any 4-Byte code of the general form 'wxyz' will be equivalent to a 5-Byte code of the form 'wxyz.', there are notable exceptions. The 4-Byte code [E333 Fear of flying], for example, corresponds to 5-Byte [E202A Fear of flying]; no [E333.] code exists in 5-Byte READ at all.