Association Between Hospital Participation in Medicare Shared Savings Program Accountable Care Organizations and...

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

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.

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.

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.

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.