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Hospital Activity publications supporting information

This page provided supporting information for the publication reports on which use Hospital Episode Statistics (HES) as their data source. This includes Hospital Admitted Patient Care Activity, Adult Critical Care Activity and Hospital Outpatient Activity. Information included in this page will be updated with relevant information however specific information relevant to an annual publication will be captured under the appropriate year.

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Hospital Episode Statistics

This page will focus on information relevant to the publications, our website contains more information about HES.

HES includes patient level data on hospital admissions and outpatient appointments for NHS trusts in England. HES includes information about private patients treated in NHS hospitals, patients who were treated in England but who were resident outside England and care delivered by treatment centres (including those in the independent sector) funded by the NHS. The Emergency Care Data Set (ECDS) is the national data set for urgent and emergency care which replaced the HES Accident and Emergency Commissioning Data Set in April 2020. This is not included in these publications.

Healthcare providers collect administrative and clinical information locally to support the care of the patient. These data are submitted to the SUS to enable hospitals to be paid for the care they deliver. HES is created from SUS to enable further secondary use of this data. HES is the data source for a wide range of healthcare analysis used by a variety of people including the NHS, government, regulators, academic researchers, the media and members of the public.

Collection of HES data is carried out on a monthly basis throughout the financial year, with a final annual refresh (AR) once the year end has passed. Each monthly collection refreshes data back to the start of the financial year, outlined in the data collection process. Provisional data for months 1 to 13 are published in the Provisional Monthly HES for Admitted Patient Care, Outpatient and Accident and Emergency Data publication and the finalised annual data is released in this publication series.

HES is a unique data source, whose strength lies in the richness of detail at patient level going back to 1989 for APC episodes, 2003 for outpatient appointments and 2007 to 2020 for A&E attendances.

HES data includes
  • specific information about the patient, such as age, gender and ethnicity
  • clinical information about diagnoses, operations and consultant specialties
  • administrative information, such as time waited, and dates and methods of admission and discharge
  • geographical information such as where the patient was treated and the area in which they live
The principal benefits of HES are in its use to
  • monitor trends and patterns in NHS hospital activity
  • assess effective delivery of care and provide the basis for national indicators of clinical quality
  • support NHS and parliamentary accountability
  • inform patient choice
  • provide information on hospital care within the NHS for the media
  • determine fair access to health care
  • develop, monitor and evaluate government policy
  • reveal health trends over time; and support local service planning
Confidentiality, Transparency and Security

Although certain information is considered especially sensitive, all information about someone's health and the care they are given must be treated confidentially and in accordance with legislation and NHS England protocols at all times.

There are a limited number of people authorised to have access to the record level data, all of whom must adhere to the written protocol issued by NHS England on the dissemination of HES data. For example, guidance is given on handling the very small numbers that sometimes occur in tables to reduce the risk that local knowledge could enable the identification of either a patient or clinician.

HES is a record level data warehouse and it contains information that could (if it was made freely available) potentially identify patients or the consultant teams treating them. In some cases record level data may be provided for medical/health care research purposes. For example, data are likely to be required by the Care Quality Commission and other such bodies. The information may be given following a stringent application procedure, where the project can justify the need and where aggregated data will not suffice. Any request involving sensitive information, or where there may be potential for identification of an individual, is referred to the appropriate governance committee. NHS England publishes a quarterly register of data releases, which includes releases of HES data.

HES data are stored to strict standards: a system level security protocol is in place. This details the security standards that are in place to ensure data are secure and only accessed by authorised users.

Cost, Performance and Respondent Burden

The production of HES data is a secondary use of data collected during the care of patients in the NHS and submitted for NHS Providers to be paid for the care they deliver. Therefore HES does not incur additional costs or burden on the providers of the data. 

Clinical classifications and coding

Diagnoses are coded in HES using the ICD10 classification.

Operative procedures are coded in HES using the OPCS classification.

Further information about these classifications, and changes to them is available. 

Accessibility and clarity

As HES is such a rich source of data it is not possible to publish aggregate tables covering all permutations of possible analysis. Underlying HES data is also made available to facilitate further analysis that is of direct relevance to users. There are no restrictions to access the published data.

All data items included in the published tables are explained in footnotes and the metadata, and NHS England publish data dictionaries for HES describing the format and possible values for all HES data items. 

These data are also accessible via an online interrogation service (for NHS users) or via our bespoke extract service Data Access Request Service (DARS). 

Admitted Patient Care Activity

This publication describes NHS Admitted Patient Care Activity and performance in hospitals in England including analysis of hospital episodes by patient demographics, diagnoses, external causes/injuries, operations, bed days, admission method, time waited, specialty and provider level analysis. The series includes publications covering data from 1998-99.

Adult Critical Care Activity

Data about Adult Critical Care (ACC) Activity is included in the Admitted Patient Care publication, following the discontinuation of the 'Hospital Adult Critical Care Activity' publication. The ACC data tables are not a designated National Statistic and they remain separate from the APC data tables. The ACC data used in this publication draws on records submitted by providers as an attachment to the admitted patient care record. These data show the number of adult critical care records during the period, with breakdowns including admission details, discharge details, patient demographics and clinical information.

Since August 2010, first the Department of Health (DH) and now NHS England has conducted censuses of the numbers of available and occupied critical care beds on the last Thursday of each month; prior to August 2010, similar censuses were conducted by DH twice a year.  These reports can be found at: https://www.england.nhs.uk/statistics/statistical-work-areas/bed-availability-and-occupancy/

Although the number of critical care beds on a given day is not directly comparable with the number of critical care periods which covered that day, a comparison between the two reveals that there are substantial differences between reporting by NHS providers to NHS England’s censuses and to the Critical Care Minimum Dataset and thus in the HES data warehouse from which this publication’s data is drawn.

In particular, there were a number of hospital providers which submitted critical care bed data to NHS England’s census but not to HES; figures reported in this publication are therefore thought to represent an undercount of the true critical care situation; conversely there were a far smaller number of providers for which there is a critical care data in HES but which did not submit any data to NHS England’s census. 

During the COVID-19 pandemic NHS England's census was suspended. As a result Table 18, which provided a comparison of NHS Census numbers and HES Critical Care Numbers has been omitted from this years report.

Over-counting of critical care periods

Most raw critical care records in the data set are associated with only one record of an APC episode, but some are associated with multiple episodes as an APC spell; to avoid multi-counting these critical care records, an algorithm has been applied to link each critical care record to the APC episode record against which it is the ‘best match’. Because of limitations in the algorithm, a small number of raw critical care records are identified as a ‘best match’ with more than one APC episode and the final presented numbers of critical care records slightly over-count the true number of critical care periods.

Default critical care start and end times

The critical care database includes fields recording the time of day at which the critical care period started and ended.

Although the times submitted are not specified to be rounded, it is clear from analysis of the data that there are rounding peaks at each multiple of 5 minutes past the hour, larger peaks at multiples of 10 minutes (and, for end times, at 59 minutes past), still larger peaks at multiples of 15 minutes, a yet larger peak at 30 minutes past the hour and the largest peak at 0 minutes past the hour; this suggests that in many cases the times are being rounded to 5, 10, 15, 30 or 60 minute boundaries.

Outpatient Activity

This publication describes NHS outpatient appointments in England, rather than the number of patients and includes data about hospital outpatient appointments by patient demographics, diagnoses, attendance type, operations, specialty, and provider level analysis. The series first reported Outpatient Activity in 2006, with releases for 2003/04.

Appointments

Records in the HES Outpatient database are called ‘appointments’. There is one row per appointment, regardless of whether or not it is attended. Appointments which are attended are called ‘attendances’. A patient is often invited to a series of appointments, the first of which is known as the ‘first appointment’. An individual patient may have more than one series of attendances in a given period, so first appointments are not the same as a count of patients.

Each record in HES includes a wide range of information including details of the patient (age, gender, geographic regions), when they were treated and what they were treated for.

UK comparison

Separate collections of hospital statistics are undertaken by Northern Ireland, Scotland and Wales. There are a number of important differences between the countries in the way that data measures are collected and classified, and because of differences between countries in the organisation of health and social services. For these reasons, any comparisons made between HES and other UK data should be treated with caution.

Hospital data for the other administrations can be found at: 

NHS England also publish other hospital activity data.

Internationally, HES and similar statistics from the devolved administrations are used to contribute to World Health Organisation (WHO), Organisation for Economic Co-operation and Development (OECD) and Eurostat compendiums on health statistics.

Suppression methodology

This publication follows standard methodology for secondary care publications in England.  

To reduce the risk of identifying individuals from small numbers, 0 with Y suppression flag or * appears in the tables for all sub-national breakdowns, where there is a value between 1 and 7. All other sub-national data has been rounded to the nearest 5.

Sensitive diagnosis and procedure codes may also be suppressed by removing breakdowns like age or implementing a similar suppression method to what is outlined above at a national level.

All calculations are completed on unrounded figures.

HES Data Quality

The quality of HES data is the responsibility of the NHS providers who submit the data to SUS. These data are required to be accurate to enable them to be correctly paid for the activity they undertake. NHS England has a well-developed data quality assurance process for the SUS and HES data and the data quality of provisional data is reported monthly to improve the quality before the annual finalisation. Details about the quality of HES data can be found below, under the relevant release section and the monthly data reports are available. 

 

Impact of COVID-19

To respond to the challenges posed by the coronavirus pandemic NHS hospitals in England were instructed to suspend all non-urgent activity for patients for parts of the 2020/21 reporting period.

This may have impacted upon how and the extent to which these types of non-urgent care activities provided that are in scope of the collection during this time.

It is also possible that behaviours around activities relating to the completion, return and processing of certain data have also been impacted when compared to earlier years data where behaviours and processes related to managing the current pandemic were not in place.

Relevance

The HES publications focus on headline information about hospital activity. Each annual publication includes a series of national tables and also provider-level breakdowns for some main areas. Most data included in the published tables are aggregate counts of hospital activity. Where averages are published, e.g. average length of stay for inpatients or caesarean rates for maternity statistics, these data are clearly labelled stating how the data has been calculated.

Accuracy and reliability

The accuracy of HES data is the responsibility of the NHS providers who submit the data to SUS. These data are required to be accurate to enable them to be correctly paid for the activity they undertake. NHS England has a well-developed data quality assurance process for the SUS and HES data. It uses an xml schema to ensure some standardisation of the data received. The use of the schema means that the data set has to meet certain validation rules before it can be submitted to SUS. NHS England leads on the schema changes and consults the data suppliers about proposed changes.

Each month NHS England makes data quality dashboards available to NHS providers to show the completeness and validity of their data submissions to SUS. This helps to highlight any issues present in the provisional data allowing time for corrections to be made before the annual data are submitted.

An external auditor, acting on behalf of the Department of Health and Social Care (DHSC), audits the data submitted to SUS to ensure NHS providers are being correctly paid by PbR for the care they provide.

NHS England validates and cleans the HES extract and derives new items. The team discusses data quality issues with the information leads in hospital trusts who are responsible for submitting data. The roles and responsibilities within NHS England are clear for the purposes of data quality assurance, i.e. to assess the quality of data received against published standards and report the results.

Data quality information for each year to date HES data set is published alongside the provisional year to date HES data, and also alongside annual publications. These specify known data quality issues each year, e.g. if a trust has a known shortfall of secondary diagnoses. The statisticians can only check the validity and format of the data and not whether it is accurate, as accuracy checking requires a level of audit capacity and capability which NHS England does not currently possess. There is also further information about HES data quality published.

NHS England also publishes a regular Data Quality Maturity Index for providers across several datasets including HES. The UK Statistics Authority conducted case studies of quality assurance and audit arrangements of administrative data sources. HES was used as a case study and further information can be found in the published report (Annex C, case study 3).

Timeliness and Punctuality

The production of the underlying annual HES data sets takes several months after the reference period. The final submission deadline for NHS providers to send annual data to SUS is normally at the end of May, almost two months after that year has finished. It then takes approximately two months to produce the HES APC data set and a further two months to complete publication production and data investigation.

In addition to annual data NHS England also publish provisional monthly HES data approximately two months after the reference period.

The final annual data includes additional data cleaning, validation and processing than the provisional monthly data.

Under-reporting at financial year boundaries

Much data associated with HES APC records, including associated critical care records, is not reliably complete until the episode or critical care period is finished. Critical care periods associated with hospital APC episodes which are still ongoing at the end of the period of coverage (i.e. at the end of March 2022) will not be reported into the system until the following financial year, when they have finished, and are therefore not included for analysis. As a result, reported figures are lower than the true figures for the full financial year, and, in particular, analysis by month (including the Table 1 in the ACC tables) will present artificially depressed figures for March.

Figures for March each year are artificially depressed as any critical care period associated with a hospital APC episode which is still on-going at the end of March will not be reported into the system until the following financial year, when it has finished.

Coherence and completeness

Users can misinterpret HES data as relating to numbers of patients, but care should be taken as the standard unit of HES data relates to hospital activity, not individuals.

In the case of outpatient treatment, it is often the case that an individual patient may be booked for a series of appointments, the first of which is distinguished from the following appointments in the data. Furthermore, an individual may be treated a number of times in the year, for the same or different conditions.

2022-23: Frimley Health NHS Foundation Trust were unable to submit data for part of the 2022-23 year. As the impact on high level national totals is assessed to be around 1%, users are advised to take this into account particularly when seeking to interpret trends over time and comparisons between regions due to the impact of this missing data. Please see further information in the 2022-23 section below.

Sensitive Clinical Codes

HES uses the World Health Organization’s ICD-10 (International Classification of Diseases and Related Health Problems) classification to record diagnosis information. The OPCS-4 (Office of Population, Censuses and Surveys: Classification of Interventions and Procedures, 4th Revision) classification is used to record details of any procedures or interventions performed, e.g. hip replacements. Some of the clinical codes have been identified as sensitive resulting in additional suppression at a national level or additional caveats. These are outlined below:

HIV: B20 - B24, Z20.6, Z21 and Z71.7 

The source of official statistics, epidemiology and surveillance of infectious diseases (including HIV/AIDS) is the Centre for Infections (CfI) at the Health Protection Agency (HPA) . Age breakdowns are not available.

IVF: Z31.2

The source of official statistics on IVF and fertility treatment is the Human Fertilisation and Embryology Authority (HFEA). Age breakdowns are not available.

Abortions:

Diagnosis: O04 to O08

Procedure: Q09.1, Q10.1, Q10.2, Q11.1-Q11.5, Q11.6, Q14.1-Q14.6, Q14.8, Q14.9

There are restrictions on using and releasing abortion statistics and official statistics for abortions are published by the Department of Health and Social Care. The numbers of abortions recorded in HES data are different to published official abortion statistics - in the HES publications, we have applied the sub-national suppression rules to the 3 and 4 character codes to ensure similar suppression to DHSC.

Procedure - Electroconvulsive Therapy (ECT): A83

"Data relating to ECT procedures/neurosurgery should be treated with caution as variation in the setting of the procedure impacts the recording of it, i.e. some trusts will perform as a day case, some as an out-patient procedure etc. ECT is often given as a course of treatment so any counts of procedures or episodes should not be described as patient counts"

 

Improvements over time

HES data is available from 1989-90 onwards whilst outpatient HES data is available from 2003-04 onwards, and A&E data is available from 2007-08. Changes to the figures over time need to be interpreted in the context of improvements in data quality and coverage (particularly in earlier years), improvements in coverage of independent sector activity (particularly from 2006-07) and changes in NHS practice.

Payment by Results (PbR) is a system whereby hospitals are paid for the number of patient treatments, known as activity, they perform and the complexity of these treatments. It was introduced in a phased way from 2003-04 onwards. In order to be paid correctly, care providers need to record the activity they perform and the clinical codes that outline the patients’ conditions and treatment.

The introduction of PbR increased private sector involvement in the delivery of secondary care and brought about some changes in clinical practice (including some procedures occurring as outpatient appointments instead of hospital admissions). It is likely that these changes will have affected trends.

This has provided a major financial incentive for care providers to ensure all of the activity they perform, and the clinical coding is fully recorded. This improved recording of information captured by HES could be one of the factors leading to the reported activity increases.

In order to manage patients’ waiting times there has been the need for additional elective operations to be performed as well as a requirement for more capacity in NHS funded care to perform this activity. In the middle of the last decade, additional capacity was brought in from the private sector via treatment centres, with the NHS funding some patients to be treated there for routine operations.

Improvements in technology and the need to increase efficiency to allow more patients to be treated have led to a reduction in the length of time patients need to stay in hospital for certain planned operations. In particular, many operations that would have involved an overnight stay at the start of the period are now routinely performed as day cases. In addition, many operations where a patient would have been admitted to hospital at the start of the period are now routinely performed in outpatients. This has led to increases in day case rates and outpatient attendances over the period.

The recent period has also seen a rise in the number of emergency admissions. One factor contributing to this is likely to be the increased demand on health services from an ageing population. Alongside this there has been the introduction of observation or medical assessment units at many hospitals to which patients arriving in A&E departments are admitted, often for around a day, to enable observation and tests to be performed on them.

2022/23

Below outlines the source of the population data for this release:

  • Age and Gender: ONS 2021 Mid-year Estimates

  • Ethnicity: ONS 2021 Census

  • IMD Decile: ONS 2020 using English Indies of Deprivation 2019

For the 2022/23 publications, the format for the outputs has been updated to meet Open Data Standards and user feedback we have received. We ran a consultation from 7th July to 18th August 2023 about the changes and would welcome feedback. The content within the publication has remained consistent with minor changes outlined below.

Admitted patient care activity

The file 'Surgery for Urogynaecological Prolapse or SUI using tape or mesh' will not be produced in the monthly or annual Hospital Episode Statistics - in collating this information, we were aware some Trusts mis-coded these procedures in Commissioning Data Set return used to produce these statistics. The decision has been made to stop releasing this data to prevent misinformation until the data quality for reporting these procedures improves.

Additionally the following outputs have been removed as they are no longer required for their original purpose:

  • Data Quality Paediatric Critical Care Analysis
  • Weekly Admissions count from report tables
  • Timeseries

Clinical coding change (ICD-10)

From October 2023 NHS England statistical publications that include the World Health Organisation (WHO) ICD-10 term ‘mental retardation’ (codes F70 – F79, F84.4 and Z81.0) will be replaced by the corresponding ICD-11 term ‘Disorder of intellectual development’. The ICD-11 term is more accurate and removes outdated and offensive terminology. Permission was granted from the World Health Organisation whilst NHS England prepare transition plans to implement ICD-11 at which time the ICD-11 terminology will be fully implemented.

The latest version of the WHO International Classification of Diseases (ICD-11) was adopted by the 72World Health Assembly in 2019 and came into effect on 1 January 2022 with transitional arrangements for Member States for at least five years.  In England, the ICD-10 5 Edition continues to be the information standard used in the NHS until further notification of implementation arrangements and roadmap.

Organisation codes

Where an organisation code changed, it was decided it to align activity against the code being used at the time it took place. For example, R0A and R0A-X may both appear - these can be summed for calculate the total for R0A.

Data quality notes

Missing data

Due to technical issues Frimley Health NHS Foundation Trust have been unable to submit data for activity occurring between the period of July 2022 to March 2023 to SUS at the time of the finalised cut of the data being taken for inclusion and reporting in HES for this period. This data quality issue will have an impact on a number of figures reported in our annual publications and will vary between metrics and a high-level impact shown below. As the impact on high level national totals is assessed to be around 1%, users are advised to take this into account particularly when seeking to interpret trends over time and comparisons between regions due to the impact of this missing data. The summary excel report includes national estimates using 2021-22 data from Frimley Health NHS Foundation Trust.

Whilst work is ongoing to establish if activity data from this period can be resubmitted to SUS user needs around the timeliness and availability of finalised HES data has meant that the data has been finalised with this and other lesser data quality impacts as logged in the report. Work is ongoing to see if activity could be resubmitted for this period to SUS in the future.

2023/24

Below outlines the source of the population data for this release:

  • Age and Gender: ONS 2021 Mid-year Estimates

  • Ethnicity: ONS 2021 Census

  • IMD Decile: ONS 2020 using English Indies of Deprivation 2019

Clinical Coding Change (OPCS-4)

This report uses OPCS-4.10 which was introduced in April 2022.

Data Quality Issues

For both Admitted Patient Care and Out-patient datasets Connect Health Limited (NMG) submitted data where the provider code was incorrectly recorded as the commissioner code. Subsequent checks showed that these commissioner codes only appeared on records associated with Connect Health Ltd and as such, these records were re-mapped to Provider Code NMG in both reports.

 

Last edited: 20 September 2024 2:42 pm