Background

HES came about in 1987 following a report on the collection and use of hospital activity information published by a steering group chaired by Dame Edith K�rner (1921-2000).

Before 1987, only a 10 per cent sample of admitted patient records were collected nationally but HES aims to collect a detailed record for each 'episode' of admitted patient care delivered in England by NHS hospitals or delivered in the independent sector but commissioned by the NHS. In 2006-07 there were 13 million admissions, resulting in nearly 15 million episodes.

Data is available for every financial year from 1989-90 onwards. During this period, the mechanisms for collecting the data have changed considerably, often in response to changes in the organisation of the NHS. For example, HES was once initially collated sub-nationally by regional health authorities. In 1996 these bodies were abolished and the NHS-Wide Clearing Service (NWCS) was set up to provide a means of transmitting the records. The work of NWCS was subsequently taken over by the National Programme for IT's (NPfIT's) Secondary Uses Service (SUS) from December 2006.

The dataset itself has been modified over time to reflect changing administrative requirements and the introduction of new clinical classifications:

• In 1995, the recording of diagnoses changed from the 9th to the 10th revision of the International Classification of Diseases (ICD), and in 1997 items were added to carry details of augmented (eg intensive) care.
• In 2006-07, the recording of procedures and interventions changed from version 4.2 to version 4.3 of the Office of Population, Censuses and Surveys (OPCS) classification of interventions and procedures, fourth revision. Further revisions were made in 2007-08 bringing us to version 4.4. All codes that were in OPCS-4.2 & 4.3 remain in 4.4.