The use of the Community Health Index (CHI) as a possible data source from which to derive small area population estimates has long been recognised. Only after work to introduce a unique patient identifier in Scotland in the mid-nineties did it become realistic to begin looking at the data and determining the feasibility of its use in small area estimates. With the approval of the then Chief Area Medical Officers and the CHI Project Board, Information Services Division (ISD) provided an extract of CHI data to National Records of Scotland (NRS) for analysis.
As stipulated by the CHI Project Board the extract excluded all patient names for data protection reasons, but included: address details to enable accurate geo-referencing where there were difficulties with the recorded postcode; the patient's CHI number to enable further developmental work on improving estimates of migration; and, details of the patient's age and sex. The use and storage of the data is monitored by the Department's Caldicott Guardian for health data, the Deputy Chief Medical Officer, and complies with the NRS's confidentiality guidelines.
In addition to the earlier agreements, a new protocol has been agreed with the 15 Directors of Public Health, which replaces the earlier agreements and provides additional support for the publication of results derived from the CHI. The new protocol also provides further restrictions on the data to ensure patient confidentiality, such as encryption of the CHI number.
As this is an experimental dataset, there may be potential applications, which are inhibited by the current restrictions, but that does not rule out reviewing the appropriateness of the restrictions at a later date.
CHI Working Group
A working group was established to evaluate the CHI and make recommendations on its use. The group was chaired by NRS with members representing local authorities, health boards, Scottish Government Health Department and the Information & Statistics Division of the Common Services Agency. The Project and working group report to the Scottish Census Advisory Group (SCAG) and the NRS Statistics Steering Group (SSG).
The working group consulted users about their requirements from small area population estimates and determined that population estimates for postcode sectors and 1999 wards, by gender and five year age groups would satisfy the large majority of user requirements. However, additional requirements for non-standard age groupings and a more flexible geography was noted and the development of the small area estimates to meet additional requirements is something that NRS will look at in the future.
As part of the recommendations made by the working group to SCAG and SSG in June 2000, these user requirements were noted and accepted by SCAG and SSG.