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Use of Quantile Regression to Determine the Impact on Total Health Care Costs of Surgical Site Infections Following Common Ambulatory Procedures

Olsen, Margaret A. PhD, MPH; Tian, Fang PhD, MPH; Wallace, Anna E. MPH; Nickel, Katelin B. MPH; Warren, David K. MD, MPH; Fraser, Victoria J. MD; Selvam, Nandini PhD, MPH; Hamilton, Barton H. PhD

doi: 10.1097/SLA.0000000000001590

Objective: To determine the impact of surgical site infections (SSIs) on health care costs following common ambulatory surgical procedures throughout the cost distribution.

Background: Data on costs of SSIs following ambulatory surgery are sparse, particularly variation beyond just mean costs.

Methods: We performed a retrospective cohort study of persons undergoing cholecystectomy, breast-conserving surgery, anterior cruciate ligament reconstruction, and hernia repair from December 31, 2004 to December 31, 2010 using commercial insurer claims data. SSIs within 90 days post-procedure were identified; infections during a hospitalization or requiring surgery were considered serious. We used quantile regression, controlling for patient, operative, and postoperative factors to examine the impact of SSIs on 180-day health care costs throughout the cost distribution.

Results: The incidence of serious and nonserious SSIs was 0.8% and 0.2%, respectively, after 21,062 anterior cruciate ligament reconstruction, 0.5% and 0.3% after 57,750 cholecystectomy, 0.6% and 0.5% after 60,681 hernia, and 0.8% and 0.8% after 42,489 breast-conserving surgery procedures. Serious SSIs were associated with significantly higher costs than nonserious SSIs for all 4 procedures throughout the cost distribution. The attributable cost of serious SSIs increased for both cholecystectomy and hernia repair as the quantile of total costs increased ($38,410 for cholecystectomy with serious SSI vs no SSI at the 70th percentile of costs, up to $89,371 at the 90th percentile).

Conclusions: SSIs, particularly serious infections resulting in hospitalization or surgical treatment, were associated with significantly increased health care costs after 4 common surgical procedures. Quantile regression illustrated the differential effect of serious SSIs on health care costs at the upper end of the cost distribution.

*Division of Infectious Diseases, Department of Medicine, Washington University School of Medicine, St. Louis, MO

HealthCore, Inc, Wilmington, DE

Olin Business School, Washington University in St. Louis, St. Louis, MO.

Reprints: Margaret A. Olsen, PhD, MPH, Division of Infectious Diseases, Washington University School of Medicine, Campus Box 8051, 660 S Euclid Ave, St. Louis, MO 63110. E-mail:

Disclosure: Funding for this project was provided by the Agency for Healthcare Research and Quality (5R01HS019713 to MAO). Additional support was provided by the Centers for Disease Control and Prevention Epicenters Program (U54CK000162 to VJF). The findings and conclusions in this document are those of the authors who are responsible for its content and do not necessarily represent the official view of Agency for Healthcare Research and Quality or Centers for Disease Control and Prevention. Access to the American Hospital Association Annual Survey of Hospitals data was provided by the Center for Administrative Data Research, supported in part by the National Center for Advancing Translational Sciences of the National Institutes of Health (UL1 TR000448), and the Agency for Healthcare Research and Quality (R24HS19455 to VJF). M.A.O. reports consultant work with Merck, Pfizer, and Sanofi Pasteur and grant funding through Cubist Pharmaceuticals, Pfizer, and Sanofi Pasteur for work outside the submitted article. D.K.W reports consultant work with Centene Corp and Novaerus Inc for work outside the submitted article. V.J.F. reports personal fees from Battelle outside the submitted article; her spouse is employed by Express Scripts. All other authors report no conflicts of interest relevant to this article.

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