Understanding pre-enrollment surgical outcomes for hospitals participating in Medicare Accountable Care Organizations

•We examined baseline characteristics of hospitals that ultimately enrolled in accountable care organizations (ACOs).•ACO-enrolling hospitals performed more surgical specialty procedures at baseline.•ACO hospitals had pre-enrollment outcomes similar to nonenrolling facilities.•Differential change in surgical quality or costs will determine the impact of ACOs.

BackgroundTo anticipate the effects of accountable care organizations (ACOs) on surgical care, we examined pre-enrollment utilization, outcomes, and costs of inpatient surgery among hospitals currently enrolled in Medicare ACOs vs nonenrolling facilities.MethodsUsing the Nationwide Inpatient Sample (2007 to 2011), we compared patient and hospital characteristics, distributions of surgical specialty care, and the most common inpatient surgeries performed between ACO-enrolling and nonenrolling hospitals before implementation of Medicare ACOs. We used multivariable regression to compare pre-enrollment inpatient mortality, length of stay (LOS), and costs.ResultsHospitals now participating in Medicare ACO programs were more frequently nonprofit (P < .001) and teaching institutions (P = .01) that performed more specialty procedures (P < .001). We observed no clinically meaningful pre-enrollment differences for inpatient mortality, prolonged length of stay, or costs for procedures performed at ACO-enrolling vs nonenrolling hospitals.ConclusionsMedicare ACO hospitals had pre-enrollment outcomes that were similar to nonparticipating facilities. Future studies will determine whether ACO participation yields differential changes in surgical quality or costs.