Using administrative data to measure the extent to which practitioners work together: "interconnected" care is common in a large cohort of family physicians.

Background: Health care practitioners in jurisdictions around the world are encouraged to work in groups. The extent to which they actually do so, however, is not often measured. The purpose of this paper is to demonstrate the potential for administrative data to measure how practitioners are interconnected through their care of patients. Our example examined the interconnected care provided by family physicians.

Methods: We defined a physician as being "interconnected" with another physician if these 2 physicians provided at least 1% of their clinic visits over a 2-year period to the same patients. We examined a cohort of 2945 primary care physicians in 309 Family Health Networks and Family Health Groups in Ontario, Canada, in 2005/06. In total, 9.3 million physician visits for 2.1 million patients were studied. For each group practice we calculated the number of interconnected physicians.

Results: Physicians had, on average, 2.2 interconnected physician partners (median=1; 25th and 75th percentile: 0, 3). Physicians saw mainly their own listed patients, and 7.9% (median=5.9%; 25th and 75th percentile: 2.4%, 11.6%) of their visits were provided to patients of their interconnected partners. The number of interconnected physicians was higher in group practices that had more physicians, but levelled to 2.5 interconnected physicians in practices with 8 or 9 physicians.

Interpretation: Routinely collected administrative data can be used to examine how health care is organized and delivered in groups or networks of practitioners. This study's concept of interconnected care provided by primary care physicians within groups could be expanded to include other practitioners and, indeed, entire health care systems using more complex network analysis methods.