Understanding the results

This area gives an introduction to the information that you are likely to see when viewing HES data.

Fields

You may see several fields as part of your data. Information about the most common of these is listed below. For information about fields not mentioned here please see the information in the Explanatory notes files or the HES Data Dictionary.

Finished episodes

A count of the number of HES records, submitted on behalf of English NHS hospital providers, that relate to episodes of admitted patient care that ended during the financial year (1 April to 31 March).

Admission episodes

Episodes that were the first in the spell of admitted patient treatment (episodes with an episode order of 1). Note that this includes patients who were admitted in previous years (ie prior to 1 April).

Emergency

Episodes with an admission method indicating the admission was an emergency (codes 21 to 24 and 28).

Waiting list

Episodes with an elective admission method indicating that the admission was from a waiting list (codes 11 and 12). Planned admissions (code 13) are not included.

Waiting time

The mean (average) or median (middle in ranking) waiting time in days for admissions from the waiting list (see above). Waiting time in HES is the period between the date of the decision to admit and the date of actual admission. Days of deferment and suspension are not yet taken into account.

The waiting time statistics produced from HES are not comparable with the official waiting list figures. The latter provide an indication of the numbers waiting to be admitted on a particular date, and how long they have been waiting up to that date.

Length of stay

The mean (average) or median (middle in ranking) of the spell duration in days. A spell is a period of continuous admitted patient care within a particular NHS trust, calculated by subtracting the admission date from the discharge date. In HES, this involves selecting records that are the last in the spell and therefore contain a discharge date. All 'discharge records' also carry an admission date because, where the spell consists of more than one episode, the admission date is carried forward from earlier episode(s) in the spell.

Day cases, which have a length of stay of zero days, are excluded from this calculation.

Age

The age of patients can be expressed as an average (mean), or records can be counted into specifed age groups. It is possible to specify the age at either the beginning, or the end, of the episode.

Bed days

The sum of all the days that patients in the group occupied hospital beds during the financial year (1 April to 31 March).

Masking small numbers

'Small numbers' in HES are the numbers 1 to 5. Sub-national analyses (those of small geographical areas) are more likely to contain small numbers, which might make it possible to identify individual patients or consultants.

When publishing HES data at a sub-national level, values from 1 to 5 and at least one other value in a row/table are masked using an asterisk (*). This is to prevent possible identification of individuals from small counts within a table.

For more information about masking small numbers, and other instances where this may apply, please see the HES Protocol.