Learning objectives: You will learn about data sources and types of information available in secondary care.
This section covers information on the main datasets available for analysing secondary care activity at individual patient level, including the strengths and weaknesses of Hospital Episodes Statistics (HES) data.
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In the NHS, data on patients' interactions with the secondary (i.e. hospital) care services is recorded on statutorily defined datasets. These are recorded by providers and exchanged with commissioners of care via electronic clearing houses. The data collected varies according to the type of interaction - outpatient attendance, admitted care, waiting for elective admission, or A&E. In each case the data to be collected is set out in the NHS Data Dictionary.
The mechanism of exchange has varied from time to time, the former NHS Wide Clearing Service (NWCS) being replaced by the Secondary User Service (SUS), though at present the data flows remains similar. NWCS/SUS data are cleaned and collated on a national basis to create HES data.
Primary Care Trusts receive data on a monthly basis. Mostly this is a measure of activity, but data on admitted patients also includes clinically coded diagnoses, operative procedures and ethnicity, enabling determination of met need and assisting in the analysis of health need and inequalities.
The NWCS/SUS data can help to identify health needs of the local population. It can be used to determine patient flows for treatment and to contribute to the analysis of health outcomes.
The most direct use of NWCS data is for monitoring contracts between primary care trusts and hospital providers. Under Payment by Results, hospitals are paid for the activity they undertake. Payment by Results is underpinned by Healthcare Resource Group (HRG) codes. HRGs are grouping of conditions and procedures that are clinically and resource-intensively similar. A national tariff is applied to each HRG code and updated each year.
The strengths of this source of secondary care data is that it is timely data, and components of NWCS data are made available to PCTs by hospital trusts on a monthly basis. The system by which it is delivered allows questioning and challenging of the data before a certain date each month.
Some of the weaknesses of this data source are that clinical coding may be of variable quality, and recording of ethnicity is sometimes a problem. In addition, outpatient datasets do not contain diagnostic information. Exchange of A&E data, although mandatory, often does not happen, as the definitions in the dataset are not considered particularly useful. Therefore, only a partial picture of A&E activity is available.
NWCS/SUS data are cleaned and collated on a national basis to create HES data. HES is a nation-wide dataset of all hospital admissions, recorded using computerised Patient Administration Systems. Each record is a subset of the record submitted by the provider to NWCS/SUS, and so defined in the NHS Data Dictionary. It is generally issued on an annual basis, though provisional data is now issued quarterly. Each record represents a period under the responsibility of a specific consultant, called a 'finished consultant episode'. A patient could have several episodes within one spell in hospital. There are hundreds of fields, including data on maternities and augmented care for patients whose care involves the use of Intensive and High Dependency care facilities. Data include:
- NHS Number
- full postcode
- date of birth
- ethnicity (more complete with each year)
- diagnosis fields
- procedures fields
- registered GP
- PCT of residence
- date of admission
- date of discharge
- method of admission
- method of discharge
Public Health Observatories are considered 'HES safe havens' and get access to sensitive fields on a national basis. Strict protocols are in place for how data can be disseminated, including clear suppression rules to prevent disclosure. Various pre-analysed reports are available free online. Dr Foster intelligence has access to NWCS and HES data, and provides data via web-based tools on hospital and PCT activity.
At a national level, the data could be used for health service planning, monitoring activity and performance, and assessing quality of care. At a local level (e.g. PCT) NCWS/SUS data is more timely, and HES is mostly used to enable national comparisons and benchmarking. Comparisons can be made between areas, for example, by calculating standardised rates. Monitoring inequalities across geographical areas, including ward level can also take place through the analysis of HES data.
Some of the strengths of this data source are that completeness of data is increasing. Standard codes (ICD10 and OPCS4) are used for diagnoses and procedures, and allow comparability between countries. For serious morbidity, HES can give prevalence of the condition across the country. More recently, HES data are becoming linked with ONS mortality data, therefore enabling greater understanding of the links between diagnosis, procedures and mortality.
Some of the weaknesses of HES and NWCS/SUS data are that they only tell us about those who have a disease and then use health care facilities. They do not give a full picture of morbidity. Specifically, they do not tell us about those people who have a disease or disability but do not seek care. Some fields are very incomplete - for example, whilst completeness of the ethnicity field has been increasing with each year, a significant proportion (10 - 15%) is filled with 'not stated'. Although outpatient data became available via HES in 2007, it comes with limitations. In addition, diagnostic data are not always completed. Other limitations can be found at the HES Online Questions about oupatient data. There were also delays in the past between NWCS outputs and HES. This has been improved because provisional data are made available on a quarterly basis, before ministerial sign-off.