Urologist Ownership of Ambulatory Surgery Centers and Urinary Stone Surgery Use

Authors

  • John M. Hollingsworth,

    1. University of Michigan, Ann Arbor, MI. Zaojun Ye, M.S., Biostatistician
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  • Zaojun Ye,

    1. University of Michigan, Ann Arbor, MI. Zaojun Ye, M.S., Biostatistician
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  • Seth A. Strope,

    1. Department of Urology, The University of Michigan, Ann Arbor, MI
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  • Sarah L. Krein,

    1. Department of Internal Medicine, Ann Arbor, MI
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  • Ann T. Hollenbeck,

    1. Detroit, MI.
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  • Brent K. Hollenbeck

    1. Department of Urology, University of Michigan, 1032B Michigan House, 2301 Commonwealth Blvd., SPC 2967, Ann Arbor, MI 48105–2967
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    • Address correspondence to Brent Hollenbeck, Department of Urology, University of Michigan, 1032B Michigan House, 2301 Commonwealth Blvd., SPC 2967, Ann Arbor, MI 48105–2967; e-mail: bhollen@med.umich.edu. John M. Hollingsworth, M.D., M.S., V.A. Scholar, is with the RWJ Clinical Scholars Program, The University of Michigan, Ann Arbor, MI. Zaojun Ye, M.S., Biostatistician, and Seth A. Strope, M.D., M.P.H., Clinical Lecturer, are with the Department of Urology, The University of Michigan, Ann Arbor, MI. Sarah L. Krein, Ph.D., R.N., Research Assistant Professor, is with the Department of Internal Medicine, Ann Arbor, MI. Ann T. Hollenbeck, J.D., is partner with the Honigman Miller Schwartz and Cohn LLP, Detroit, MI.


Abstract

Objectives. To understand how physician ownership of ambulatory surgery centers (ASCs) relates to surgery use.

Data Source. Using the State Ambulatory Surgery Databases, we identified patients undergoing outpatient surgery for urinary stone disease in Florida (1998–2002).

Study Design. We empirically derived a measure of physician ownership and externally validated it through public data. We employed linear mixed models to examine the relationship between ownership status and surgery use. We measured how a urologist's surgery use varied by the penetration of owners within his local health care market.

Principal Findings. Owners performed a greater proportion of their surgeries in ASCs than nonowners (39.6 percent versus 8.0 percent, p<.001), and their utilization rates were over twofold higher ( p<.001). After controlling for patient differences, an owner averaged 16.32 (95 percent confidence interval [CI], 10.98–21.67; p<.001) more cases annually than did a nonowner. Further, for every 10 percent increase in the penetration of owners within a urologist's local health care market, his annual caseload increased by 3.32 (95 percent CI, 2.17–4.46; p<.001).

Conclusions. These data demonstrate a significant association between physician ownership of ASCs and increased surgery use. While its interpretation is open to debate, one possibility relates to the financial incentives of ownership. Additional work is necessary to see if this is a specialty-specific phenomenon.

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