Catalogue description Department of Health: Public Health Common Dataset

Hardware: For the 1988 to 1996 PHCDS the data was distributed on 3.5 inch floppy disks. (The 1990 User Guide states that HAs could request the data on 5.25 inch disks.) The number of disks per year differed depending on the number of files. For the 1997 and 1998 PHCDS the data was distributed on a CD-ROM.

Operating System: Microsoft DOS (MS-DOS) and Microsoft Windows.

Application Software: For 1988 to 1995 the data was distributed in Symphony (WR1) spreadsheets. To read the data a copy of Symphony (version 1.1 or upwards), or Lotus 1-2-3, or a spreadsheet package that could import Lotus files, was required.

For 1996 the data was distributed as compressed (ZIP) files. These files had to be copied onto the hard disk of a PC and then uncompressed. The uncompressed files were Lotus 1-2-3 (WK3) files.

For 1997 the data was distributed as Lotus 1-2-3 (WK3) files.

For 1998 and 1999 the PHCDS data was distributed as Lotus 1-2-3 (WK4) files; the Compendium data was supplied in two formats, Lotus 1-2-3 (WK3) and Microsoft Excel 97.

Logical structure and schema: One table has been created for each spreadsheet file. The structure of each table reflects the structure of the original file. Each dataset consists of the tables relating to that year of the PHCDS. Within each year tables are grouped by topic, e.g. tables on population are grouped together. Some topics are only available for some years, which reflects the development of the PHCDS. To allow users to combine fields from more than one file, relationships were set up by NDAD between all tables (for the same type of NHS administrative area) within a topic. For example in the 1988 dataset, all tables within the first topic (Population and Demography) are linked.

How data was originally captured and validated: The organisations that provided data for the PHCDS include OPCS's successor, the Office for National Statistics (ONS), the DoH and the NHS via RHAs, HAs and hospitals. The major data collection/statistical systems that provide source data for the PHCDS include:

• Vital Statistics - data on population, births, deaths, fertility and mortality
• Death certification - registration of deaths and medical certificate of cause of death
• Census - count of all people and households (usually every 10 years)
• General Household Survey - continuous survey of a sample of people resident in private households
• Health Survey for England - survey designed to monitor the nation's health
• National Food Survey - continuous survey of a sample of people resident in private households
• Cancer registration minimum data set - collected via regional and national cancer registries
• British Isles Network of Congenital Anomalies Register (BINOCAR) and National Down Syndrome Cytogenetic Register
• KC50 - statistical return on vaccinations against communicable diseases
• Hospital Episodes System (HES) - holds data on consultant episodes for hospital in-patients

Generally, the data used in the PHCDS was validated by the original data collectors before being used. The source data for the PHCDS was usually processed by the organisations producing the PHCDS to create the indicators. Many indicators are a rate per population, so that HAs can be compared. The processing methodology of each indicator is described in the User Guides included with the dataset documentation.

Constraints on the reliability of the data: There are a small number of tables in which some figures are displayed as percentages within the original spreadsheet (when viewed via Excel) but are exported to CSV as figures between 0 and 1, and are therefore held as such.

Validation performed after transfer: Details of the content and transformation validation checks performed by NDAD on each dataset are recorded in the catalogues of individual datasets.

The Public Health Common Dataset (PHCDS) has been commissioned annually by the Department of Health (DoH) for the National Health Service (NHS) since 1988/89. Within the Department of Health, the Public Health Group has responsibility for the development of the Our Healthier Nation public health strategy across government. Within the NHS Executive (NHSE), the NHS Public Health Development Unit (PHDU) is responsible for public health strategy and function in the NHS. The PHCDS is a compendium of data across a range of nationally identified items with a relevance to public health. The DoH commissions external organisations to create the PHCDS on its behalf.

The 1988 PHCDS was produced by the Epidemiology and Public Health Research Unit at the University of Surrey. By the 1991 PHCDS this organisation had changed its name to the Institute of Public Health, and by the 1996 PHCDS it had become the National Institute of Epidemiology. The 1998 PHCDS was produced by the Centre for Public Health Monitoring at the London School of Hygiene and Tropical Medicine (LSHTM).

The purpose of the PHCDS has developed from helping directors of public health agencies produce their annual reports, to encompass monitoring progress in achieving Health of the Nation (HoN) targets, and subsequently Our Healthier Nation targets. The PHCDS also monitors clinical outcomes. The Public Health Common Data Set (known as the Compendium of Clinical and Health Indicators since 1998) provides health authorities with a 'common currency' for studying and comparing information about health.