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Multispecialty physician networks in Ontario

Therese A Stukel, Richard H Glazier, Susan E Schultz, Jun Guan, Brandon M Zagorski, Peter Gozdyra, David A Henry

ABSTRACT

Background: Large multispecialty physician group practices, with a central role for primary care practitioners,
have been shown to achieve high-quality, low-cost care for patients with chronic disease. We assessed the extent
to which informal multispecialty physician networks in Ontario could be identified by using health administrative
data to exploit natural linkages among patients, physicians, and hospitals based on existing patient flow.

Methods: We linked each Ontario resident to his or her usual provider of primary care over the period from fiscal
year 2008/2009 to fiscal year 2010/2011. We linked each specialist to the hospital where he or she performed the
most inpatient services. We linked each primary care physician to the hospital where most of his or her ambulatory
patients were admitted for non-maternal medical care. Each resident was then linked to the same hospital as his or
her usual provider of primary care. We computed “loyalty” as the proportion of care to network residents provided
by physicians and hospitals within their network. Smaller clusters were aggregated to create networks based on a
minimum population size, distance, and loyalty. Networks were not constrained geographically.

Results: We identified 78 multispecialty physician networks, comprising 12 410 primary care physicians, 14 687
specialists, and 175 acute care hospitals serving a total of 12 917 178 people. Median network size was 134 723 residents,
125 primary care physicians, and 143 specialists. Virtually all eligible residents were linked to a usual provider
of primary care and to a network. Most specialists (93.5%) and primary care physicians (98.2%) were linked
to a hospital. Median network physician loyalty was 68.4% for all physician visits and 81.1% for primary care
visits. Median non-maternal admission loyalty was 67.4%. Urban networks had lower loyalties and were less selfcontained
but had more health care resources.

Interpretation: We demonstrated the feasibility of identifying informal multispecialty physician networks in Ontario
on the basis of patterns of health care–seeking behaviour. Networks were reasonably self-contained, in that
individual residents received most of their care from providers within their respective networks. Formal constitution
of networks could foster accountability for efficient, integrated care through care management tools and quality
improvement, the ideas behind “accountable care organizations.”

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