Construction and use of mapping techniques to describe the geographical distribution of medication dispensing for the secondary prevention of atherosclerotic CVD in New Zealand: VIEW-2.

BACKGROUND

The Health Quality and Safety Commission (HQSC) is developing Atlases of Healthcare Variation in New Zealand. We were invited to create and map the sociogeographic distribution of medication dispensing patterns among people with atherosclerotic cardiovascular disease (CVD).

METHODS

We developed two interactive online atlas 'templates' demonstrating geographical variations in CVD medication dispensing using InstantAtlas. Each template provides stratified results in tabular, graphical and map format. In the 'Standard' template proportions were mapped according to standard deviations from the mean, while the 'Advanced' template used a 'heat-map' classification to show DHB-level variations. Furthermore, we added commentaries describing the variations present and provided questions of potential interest for users.

RESULTS

The Standard template was best suited for DHB-level variations relative to a specific age, gender, or ethnic group but less effective for showing comparisons between two groups (e.g. Maori and Pacific). By contrast, the fixed legend and 'radar plot' in the Advanced template highlighted variations in medication dispensing rates geographically and sociodemographically more effectively.

CONCLUSIONS

Geographical mapping of unwarranted variations in effective care requires careful consideration. Our experience from developing this CVD atlas is documented here for developers of other components of the Atlas of Healthcare Variation in New Zealand.