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Publication, Part of

Hospital Accident & Emergency Activity 2019-20

Publication Date:
Geographic Coverage:
Date Range:
01 Apr 2019 to 31 Mar 2020

Data Quality Statement


HES data includes patient level data on hospital admissions, outpatient appointments and A&E attendances for all NHS trusts in England. It covers acute hospitals, mental health trusts and other providers of hospital care. HES includes information about private patients treated in NHS hospitals, patients who were resident outside England and care delivered by treatment centres (including those in the independent sector) funded by the NHS.

Healthcare providers collect administrative and clinical information locally to support the care of the patient. This data is submitted to 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.

HES is a unique data source, whose strength lies in the richness of detail at patient level going back to 1989 for Admitted Patient Care (APC) episodes, 2003 for outpatient appointments and 2007 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
  • support local service planning

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, this data is 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 the Secondary Uses Service (SUS). This data is required to be accurate to enable providers to be correctly paid for the activity they undertake.

SUS is the single, comprehensive repository for healthcare data in England which enables a range of reporting and analyses to support the NHS in the delivery of healthcare services.

When a patient or service user is treated or cared for, information is collected which supports their treatment. This information is also useful to commissioners and providers of NHS-funded care for 'secondary' purposes - purposes other than direct or 'primary' clinical care - such as:

  • healthcare planning
  • commissioning of services
  • national tariff reimbursement
  • development of national policy

SUS is a secure data warehouse that stores this patient-level information in line with national standards and applies complex derivations which support national tariff policy and secondary analysis. 

A list of mandatory and optional fields for submission in in the Commissioning Data Set (CDS) is provided within the NHS Model and Data Dictionary:

A&E: CDS V6-2 Type 010 – Accident and Emergency CDS

ECDS: CDS V6-2 Type 011 – Emergency Care CDS

NHS Digital 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 Digital leads on the schema changes and consults the data suppliers about proposed changes.

Each month NHS Digital create 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 is submitted.

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

NHS Digital 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 Digital are clear for the purposes of data quality assurance, to assess the quality of data received against published standards and report the results.

Data quality information for each year to date HES dataset is published alongside the provisional year to date HES data, and also alongside annual publications. These specify known data quality issues each year and where a trust has a known shortfall of secondary diagnoses. The statisticians can only check the validity and format of the data and not whether they are accurate, as accuracy checking requires a level of audit capacity and capability which NHS Digital does not currently possess.

There is also further information about HES data quality published online:

NHS Digital also publishes an annual report The Quality of Nationally Submitted Health and Social Care Data, which highlights issues around the recording of the underlying data that is used for HES, as well as examples of good and poor practice, and a regular Data Quality Maturity Index for providers across several datasets including HES:

Data Quality Note

Detailed information about data quality of data items, and completeness of provider data submissions can be accessed via the following link:

A&E HES data has been available since 2007-08 and during those early years data completeness was known to be an issue.

Records submitted via the ECDS data set use SNOMED coding and do not always directly match to the current A&E data set. In order to retain the HES A&E data set, SNOMED codes have been mapped to A&E from various ECDS fields. This has resulted in some noticeable differences in attendances for some of fields when comparing 2018-19 and 2019-20 data.

Data Completeness

Users should note there was a reduction in attendances at each of the four Home Nation Emergency Departments from March 2020, at the start of the COVID-19 outbreak.

There are some definitional differences between A&E HES data and MSitAE data. The main difference is that MSitAE data does not include attendances where the A&E appointment has been pre-arranged. Therefore, where A&E HES is compared directly with MSitAE, planned follow-up attendances are excluded.

Overall coverage in HES has increased from 2018-19, however the data completeness for a number of key fields has reduced from the previous year.  This is due to the increase of records submitted to ECDS, and being mapped across to A&E.

Codes are considered to be valid if they matched to one of the A&E CDS data dictionary values for the specified field and were considered invalid if they did not match one of the data dictionary values. Where a field has a null value it is considered invalid.

Multiple diagnosis, investigation and treatment codes can be submitted within the dataset. The analysis contained within this report only looks at the first (or primary) diagnosis, investigation and treatment codes submitted. It also only uses the first two characters of these codes covering the diagnosis condition, investigation and treatment sections of the six-character codes. This is due to quality issues with these clinical fields.

Final and Provisional Data Comparison

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.

‘Month 13’ represents the provisional full year data and was published in June 2020. Hospital providers and the NHS Digital HES Data Quality team work to improve the quality and completeness of the data in order to produce the final AR data used in this report, as described in the Accuracy and Reliability Section above.

The table below shows the differences between the Month 13 provisional data and the final AR data

Comparing Month 13 and Annual Refresh Data, 2019-20
Comparing Month 13 and Annual Refresh Data, 2019-20
Timeliness and Punctuality

HES data is published as early as possible. 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 data set and a further month to complete publication production and data investigation.

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

The final annual data includes some additional data cleaning and more up-to-date reference data used with the derivations, compared to Month 13 data.

Monthly Variation in Submitted Records, 2019-20

The chart below shows the number of attendances occurring in the last three submission periods of 2019-20, including annual refresh. The number of records per month of activity generally increases as more submissions are made; the completeness of the data improves over time.

Updated reference data was applied to annual refresh and does change some derived fields. A small number of providers’ data were taken after the M13 inclusion date which gives slightly different overall record counts.

Users should note there was a reduction in attendances from March 2020, at the start of the COVID-19 outbreak.

Download the data for this chart Monthly Variation in Submitted Records, 2019-20
Coherence and Comparability

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 A&E data, this is presented as attendances, which may include people attending more than once in the reporting period.

UK Comparisions

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 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.

ONS used to produce UK Health Statistics which contained key figures about the use of health and social services, including hospital admitted patient activity and waiting times across the UK. The last version of this discontinued series can be found at:

Other UK Data

Hospital data for the other administrations can be found at:

  • Northern Ireland – Hospital Statistics
  • Scotland – Hospital Care
  • Wales – Health and social care statistics

NHS England also publish other hospital activity data:

Wider International Comparisons

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.

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.

Comparisons of Annual HES Data

Care should be taken when comparing annual HES data over time, as improvements in coverage in HES will contribute alongside growth from increased activity through the years.

Extra care should be taken when looking at clinical data, as changes in NHS practices (such as the introduction of new procedures and interventions) can have an effect on changes through time.

Comparisons of Annual data for certain fields and reported activity is now no longer directly comparable since the phased introduction of the new Emergency Care Data Set commenced in October 2017. Since this point urgent and emergency care providers have been asked to submit data to the ECDS. Those that do this will no longer submit data via the A&E Commissioning Data Set (CDS 010), which means that their A&E data would no longer be automatically processed into Hospital Episode Statistics (HES) for that provider. However in order to seek a continuity in the data during this transition period during the phased implementation of ECDS NHS Digital with guidance from nominated representatives from the Royal College of Emergency Medicine (RCEM) put in place a mapping process of reported activity within ECDS to A&E CDS to allow data to be populated for the providers who have switched to submitting ECDS so that data can still be used in this and other statistical releases.

Details of this mapping methodology can be found within the Technical Output Specification Document on the ECDS project website.

Additional detail may be found in the following methodological change notice paper published by NHS Digital

The change should not impact upon overall total counts of activity presented within the data. However, changes are expected in the composition of data from those trusts that have submitted to ECDS and have subsequently been mapped to the A&E Commissioning Data Set format. A key driver of the ECDS is to improve current clinical data quality and make the data that is captured compatible with other modern data sets. Therefore, several codes that either represent clinical practice that no longer takes place in the A&E department or the coding adds no clinical value have been retired. Additionally, under SNOMED there is no ‘other’ code therefore it will no longer be possible for activity submitted by organisations via ECDS to be mapped to a small number of codes. The codes and fields identified as being affected are listed in the methodological change paper referenced earlier. Comparisons across time of activity before and after the 1st October 2017 of activity using these codes or using other codes within these specific fields therefore may not be comparable. Further analyses on the impact of the introduction of ECDS to this reporting accompanies this statistical release.

Early Years’ Data

The first A&E submission from providers in England was for the 2007-08 financial year; these reports were experimental until 2012-13.

Changes to Organisation Codes and Geographical Boundaries

The Organisation Data Service (ODS) is responsible for the publication of all organisation and practitioner codes and national policy and standards with regard to the majority of organisation codes.

For more information about the ODS and changes to organisation codes and geographical boundaries visit:

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 accessing the published data.

Trade-offs between Quality Components

Providers have the opportunity to submit data each month, which is centrally assessed for data quality and issues is reported back to providers in order to give an opportunity to address any issues found. The dataset is then finalised for the full financial year, and issues remaining after that point are published on NHS Digital’s website, but no attempt is made to amend the data.

Assessment of User Needs and Perceptions

Users of the data and this publication are encouraged to report and feedback their views and suggestions. We have a dedicated e-mail, for users to e-mail their queries or concerns and if anything is identified as being unclear, we address that as soon as we possibly can.

We consult users when proposing significant changes to the content of or methodologies used in the publications. NHS Digital conducted a wider consultation exercise on all its publications and services, including HES, and the outcome is available to all.

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.

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 Digital 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 Digital 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 is 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 Digital publishes a quarterly register of data releases, which includes releases of HES data.

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

Last edited: 4 September 2020 11:51 am