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Association Between Hospital Participation in Medicare Shared Savings Program Accountable Care Organizations and Readmission Following Major Surgery

Borza, Tudor MD, MS*,†; Oerline, Mary K. MS; Skolarus, Ted A. MD, MPH*,†,‡; Norton, Edward C. PhD§,¶,||; Dimick, Justin B. MD, MPH**; Jacobs, Bruce L. MD, MPH††; Herrel, Lindsey A. MD, MS*,†; Ellimoottil, Chad MD, MS*,†; Hollingsworth, John M. MD, MS; Ryan, Andrew M. PhD§,¶; Miller, David C. MD, MPH*,†; Shahinian, Vahakn B. MD, MS‡‡; Hollenbeck, Brent K. MD, MS*,†

doi: 10.1097/SLA.0000000000002737

Objective: To evaluate the effect of Medicare Shared Savings Program accountable care organizations (ACOs) on hospital readmission after common surgical procedures.

Summary Background Data: Hospital readmissions following surgery lead to worse patient outcomes and wasteful spending. ACOs, and their associated hospitals, have strong incentives to reduce readmissions from 2 distinct Centers for Medicare and Medicaid Services policies.

Methods: We performed a retrospective cohort study using a 20% national Medicare sample to identify beneficiaries undergoing 1 of 7 common surgical procedures—abdominal aortic aneurysm repair, colectomy, cystectomy, prostatectomy, lung resection, total knee arthroplasty, and total hip arthroplasty—between 2010 and 2014. The primary outcome was 30-day risk-adjusted readmission rate. We performed difference-in-differences analyses using multilevel logistic regression models to quantify the effect of hospital ACO affiliation on readmissions following these procedures.

Results: Patients underwent a procedure at one of 2974 hospitals, of which 389 were ACO affiliated. The 30-day risk-adjusted readmission rate decreased from 8.4% (95% CI, 8.1–8.7%) to 7.0% (95% CI, 6.7–7.3%) for ACO affiliated hospitals (P < 0.001) and from 7.9% (95% CI, 7.8–8.0%) to 7.1% (95% CI, 6.9–7.2%) for non-ACO hospitals (P < 0.001). The difference-in-differences of the 2 trends demonstrated an additional 0.52% (95% CI, 0.97–0.078%) absolute reduction in readmissions at ACO hospitals (P = 0.021), which would translate to 4410 hospitalizations avoided.

Conclusion: Readmissions following common procedures decreased significantly from 2010 to 2014. Hospital affiliation with Shared Savings ACOs was associated with significant additional reductions in readmissions. This emphasis on readmission reduction is 1 mechanism through which ACOs improve value in a surgical population.

*Department of Urology, Division of Oncology, University of Michigan, Ann Arbor, MI

Dow Division for Urologic Health Service Research, University of Michigan, Ann Arbor, MI

VA Health Services Research & Development, Center for Clinical Management Research, VA Ann Arbor Healthcare System, Ann Arbor, MI

§Department of Health Management and Policy, University of Michigan, Ann Arbor, MI

Department of Economics, University of Michigan, Ann Arbor, MI

||National Bureau of Economic Research, Cambridge, MA

**Department of Surgery, Center for Healthcare Outcomes and Policy, University of Michigan, Ann Arbor, MI

††Department of Urology, University of Pittsburgh Medical Center, Pittsburgh, PA

‡‡Department of Internal Medicine, University of Michigan, Ann Arbor, MI.

Reprints: Tudor Borza, MD, MS, Dow Division for Health Services Research, Department of Urology, University of Michigan, 2800 Plymouth Road, Building 16, Ann Arbor, MI 48109-2800. E-mail:

This study was supported by National Institute on Aging R01 AG048071 (B.K.H.) and R01 AG039434 (J.B.D.), National Cancer Institute Grant R01 CA174768 (D.C.M.), T32 CA180984 (T.B.), Agency for Health Care Research and Quality R01 HS024728 (J.M.H.) and R01 HS024525 (J.M.H.).

Funders had no role in the design and conduct of the study, collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

The views expressed in this article do not reflect the views of the federal government.

Dr. Dimick has a financial interest in Arbormetrix, Inc.

The authors report no conflicts of interest.

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