How can the spatial equity of health services be defined and measured? A systematic review of spatial equity definitions and methods

Background Spatial equity analysis has been carried out in a variety of contexts and on a range of health services. However, there is no clear consensus on spatial equity definitions or measures. This review seeks to summarize spatial equity definitions and methods of analysis. Methods We systematically searched two electronic databases and six journals for papers providing a definition of spatial equity or performing a spatial equity analysis on health services. Studies were classified according to four definition themes: (1) distributional fairness; (2) needs-based distribution; (3) focus on outcomes or causes and (4) none provided. Results Seventy-five studies met our inclusion criteria. Sixty-one papers provided a definition of spatial equity, while a further 14 papers analysed the spatial equity of health services without providing a definition. Most authors used a needs-based definition of spatial equity, while the Gini coefficient was the most commonly used equity measure. However, analysis approaches varied according to the definition provided by each paper. Among the needs-based definitions, spatial autocorrelation was the most common spatial equity measure. Conclusions To our knowledge, this is the first systematic review summarizing spatial equity definitions and analysis methods. A lack of consensus on definitions and measures persists. The classification of measures according to definition themes makes this review a useful tool for planning and interpreting spatial equity investigations. Future research should examine the impact different measures of accessibility and need have on the results of spatial equity research.