A comparison of measures of access to child health clinics and the implications for modelling the location of new clinics

Objective: To determine whether measurement of access to existing child health clinics, and modelled location of new clinics, was affected by the spatial definitions of the target population. Method: Populations requiring childhood screening services were defined as located at individual households, and at geographic and population-weighted centroids of small and large areas. Straight-line and network distances were measured and compared from these origins to varying numbers of existing clinics. The same origins were used to model sets of locations for new clinics, and access levels were again compared. Results: Travel distances for 82,499 annual baby-visits to 140 existing clinics were between 136,000 km and 84,000 km, depending on origin definition. An analysis based on small area centroid data was as accurate as one based on household data. Planning solutions for new clinics located on the basis of few large areas, with populations centred at spatially defined centroids, resulted in poorer access for the population (231,000 km of travel) than one based on many small areas with populations centred at population weighted centroids (194,000 km of travel). Implications: Public access to health facilities will be improved if decisions about their locations are aided by the application of spatial analysis techniques based on small area definitions.