[Patient-sharing networks : New approaches in the analysis and transformation of geographic variation in healthcare].

The analysis of geographic variations has spurred arguments that area of residence determines access to and quality of healthcare. In this paper we argue that unwarranted geographic variations can be traced back to actions of individual patients and their healthcare providers (doctors, hospitals). These actors interact in a complicated web of shared responsibilities. Designing effective interventions to reduce unwarranted geographic variations may therefore depend on methods to identify these interactions and communities of providers with a shared accountability. In the US, Canada, and Germany, routine data have been used to identify self-organized informal or virtual networks of physicians and hospitals, so-called patient-sharing networks (PSNs). This is an emerging field of analysis. We attempt to provide a brief report on the state of work in progress. It can be shown that variation between PSNs in a given area is effectively greater than variation between regions. While this suggests that reducing unwarranted variation needs to start at the level of PSN, methods to identify PSNs still vary widely. We compare epidemiological approaches and approaches based on graph theory and social network analysis. We also present some preliminary findings of exploratory analyses based on comprehensive claims data of physician practices in Germany. Defining PSNs based on usual provider relationships helps to create distinctive patient populations while PSNs may not be mutually exclusive. Social network analysis, on the other hand, appears better equipped to differentiate between provider communities with stronger and weaker ties; it does not yield distinctive patient populations. To achieve accountability and to support change management, analytic methods to describe PSNs still need refinement. There are first projects in Germany which use PSNs as an intervention platform in order to achieve improved cooperation and reduce unwarranted variation in their care processes.