A national facility for small area disease mapping and rapid initial assessment of apparent disease clusters around a point source: the UK Small Area Health Statistics Unit.

BACKGROUND: Reports of disease clusters are often received by district health authorities and are, in some cases, associated with concerns about a pollution source. The Small Area Health Statistics Unit (SAHSU) has developed a Rapid Inquiry Facility, which will produce an estimated relative risk for any given condition for the population within defined areas around a point source, relative to the population in a local reference region. The system can also facilitate the production of annual reports and other health studies for Departments of Public Health Medicine through the creation of ward-level maps to illustrate disease variation across small areas.
METHODS: The facility uses routinely collected morbidity, mortality and population data at a small area scale, together with the computing facilities and expertise necessary to run such analyses quickly and efficiently. Using this facility SAHSU can supply a report within three working days. To aid interpretation, smoothed small area maps that account for sampling variability in the observed data can also be produced.
RESULTS: The paper reports on two case studies where the pilot system has been utilized by health authorities for both point source analyses and small area disease mapping.
CONCLUSIONS: We believe that this facility would be of considerable use to districts. The local knowledge and expertise of the local public health specialist is essential in the interpretation and presentation of the facility's output. Feedback from public health specialists is helping SAHSU refine the output of the facility, so as to make the information presented as comprehensive and as useful as possible.