Notes:

1. Assignment of episodes to years: Years are assigned by the end of the first period of care in a patient's hospital stay.

2. Finished admission episodes: A finished admission episode is the first period of in-patient care under one consultant within one health care provider. Please note that admissions do not represent the number of in-patients, as a person may have more than one admission within the year.

3. Cause code—stab wounds¹: The cause code is a supplementary code that indicates the nature of any external cause of injury, poisoning or other adverse effects. HES has used the following ICD-10 external cause codes when referring to stab wounds.

Stab wounds¹:

W26—Contact with knife, sword or dagger.

X99—Assault by sharp object.

4. Data quality: Hospital episode statistics (HES) are compiled from data sent by over 300 NHS Trusts and Primary Care Trusts (PCTs) in England. The NHS Information Centre for health and social care liaises closely with these organisations to encourage submission of complete and valid data and seeks to minimise inaccuracies and the effect of missing and invalid data via HES processes. While this brings about improvement over time, some shortcomings remain.

5. Assessing growth through time: HES figures are available from 1989-90 onwards. During the years that these records have been collected by the NHS there have been ongoing improvements in quality and coverage. These improvements in information submitted by the NHS have been particularly marked in the earlier years and need to be borne in mind when analysing time series. Some of the increase in figures for later years (particularly 2006-07 onwards) may be due to the improvement in the coverage of independent sector activity. Changes in NHS practice also need to be borne in mind when analysing time series. For example, a number of procedures may now be undertaken in outpatient settings and may no longer be accounted for in the HES data. This may account for any reductions in activity over time.

6. Ungrossed data: Figures have not been adjusted for shortfalls in data (i.e. the data are ungrossed).

7. Low numbers: Due to reasons of confidentiality, figures between 1 and 5 have been suppressed and replaced with “*” (an asterisk).

8. Primary care trust (PCT) and strategic health authority (SHA) data quality: PCT and SHA data was added to historic data-years in the HES database using 2002-03 boundaries, as a one-off exercise in 2004. The quality of the data on PCT of Treatment and SHA of Treatment is poor in 1996-97,1997-98 and 1998-99, with over a third of all finished episodes having missing values in these years. Data quality of PCT of GP practice and SHA of GP practice in 1997-98 and 1998-99 is also poor, with a high proportion missing values where practices changed or ceased to exist. There is less change in completeness of the residence-based fields over time, where the majority of unknown values are due to missing postcodes on birth episodes. Users of time series analysis including these years need to be aware of these issues in their interpretation of the data.

Sources:

Hospital Episode Statistics (HES), The NHS Information Centre for Health and Social Care

Primary Care Trust (PCT) and Strategic Health Authority (SHA) Population data

1997-2006 SHA Mid Year Estimates, 2001 Census based. Source: ONS Population Estimates Unit

2002-06 PCT population data is calculated out on the new ONS methodology and are the recognised population estimates. Previous methodology was applied to data of 2001 only but has been disregarded for the purpose of this PQ as the totals of the old methodologies and new methodologies will not be the same.