Funnel plots and choropleth maps in cancer risk communication: a Delphi study

In the last decades, the issues related to health risk communication to stakeholders and citizens involving health care practitioners and local political authorities have been increasingly debated. The study evaluated an alternative strategy to communicate cancer risk to local communities, involving an expert panel of public health operators in comparing two different graphic tools, Funnel Plot and Choropleth map.

A Delphi method process was implemented to achieve a unified consensus on an expert panel of public health operators with regard to weaknesses and strengths of the Funnel Plot and the Choropleth map as tools for cancer risk communication to local communities and other stakeholders.

Participants were asked to score the efficacy of the two tools using a scale. Six properties were explored through two consecutive consensus rounds. Scales were used to calculate frequencies and the content validity ratio for each domain within the consensus rounds.

After the two consecutive rounds, participants expressed their preference in favour of the Choropleth map for its ability to define the spatial location of the risk and to locate any potential cluster, while reaching a consensus with regard to the Funnel Plot properties to identify hot spots, displaying the scope of the phenomenon under investigation, and to show the precision of estimates and communicating the significance of estimates.

The Delphi process allowed us to conclude that Funnel Plot could be used as a complement to the current and commonly used graphical and visual formats to effectively communicate cancer epidemiological data to communities and local authorities, representing a useful tool for empowering the general population.