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. 2015 May 14;372(20):1927-36.
doi: 10.1056/NEJMsa1414929. Epub 2015 Apr 15.

Performance differences in year 1 of pioneer accountable care organizations

J Michael McWilliams  1 , Michael E Chernew, Bruce E Landon, Aaron L Schwartz
Affiliations

Performance differences in year 1 of pioneer accountable care organizations

J Michael McWilliams et al. N Engl J Med. .

Abstract

Background: In 2012, a total of 32 organizations entered the Pioneer accountable care organization (ACO) program, in which providers can share savings with Medicare if spending falls below a financial benchmark. Performance differences associated with characteristics of Pioneer ACOs have not been well described.

Methods: In a difference-in-differences analysis of Medicare fee-for-service claims, we compared Medicare spending for beneficiaries attributed to Pioneer ACOs (ACO group) with other beneficiaries (control group) before (2009 through 2011) and after (2012) the start of Pioneer ACO contracts, with adjustment for geographic area and beneficiaries' sociodemographic and clinical characteristics. We estimated differential changes in spending for several subgroups of ACOs: those with and those without clear financial integration between hospitals and physician groups, those with higher and those with lower baseline spending, and the 13 ACOs that withdrew from the Pioneer program after 2012 and the 19 that did not.

Results: Adjusted Medicare spending and spending trends were similar in the ACO group and the control group during the precontract period. In 2012, the total adjusted per-beneficiary spending differentially changed in the ACO group as compared with the control group (-$29.2 per quarter, P=0.007), consistent with a 1.2% savings. Savings were significantly greater for ACOs with baseline spending above the local average, as compared with those with baseline spending below the local average (P=0.05 for interaction), and for those serving high-spending areas, as compared with those serving low-spending areas (P=0.04). Savings were similar in ACOs with financial integration between hospitals and physician groups and those without, as well as in ACOs that withdrew from the program and those that did not.

Conclusions: Year 1 of the Pioneer ACO program was associated with modest reductions in Medicare spending. Savings were greater for ACOs with higher baseline spending than for those with lower baseline spending and were unrelated to withdrawal from the program. (Funded by the National Institute on Aging and others.).

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Figures

Figure 1
Figure 1. Differential Changes in Medicare Spending for Pioneer Accountable Care Organizations (ACOs) versus the Control Group, According to ACO Characteristics
Adjusted differential changes in total quarterly Medicare spending from the precontract period (2009 through 2011) to the postcontract period (2012) for beneficiaries attributed to Pioneer ACOs versus the control group (beneficiaries attributed to non-ACO taxpayer identification numbers who were living in hospital referral regions served by Pioneer ACOs) are shown for subgroups of ACOs defined according to financial integration between hospitals and physician groups versus no financial integration between those entities, baseline (2008) spending for the control group in ACO service areas, ACO baseline spending relative to local average spending in the control group, and withdrawal from or continued participation in the Pioneer program. Estimates are shown with 95% confidence intervals (error bars). P values for tests of differences in savings between ACO subgroups (interaction tests) are shown. Because of correlations between estimates, differences between subgroups may be significant even if confidence intervals overlap.
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References

    1. Centers for Medicare and Medicaid Innovation. Pioneer accountable care organization (ACO) model request for application. 2011 ( http://innovations.cms.gov/Files/x/Pioneer-ACO-Model-Request-For-Applica...).
    1. Center for Medicare and Medicaid Innovation. Pioneer ACO alignment and financial reconciliation methods. 2011 ( http://innovations.cms.gov/Files/x/Pioneer-ACO-Model-Benchmark-Methodolo...).
    1. Centers for Medicare and Medicaid Services. Guide to quality performance scoring methods for accountable care organizations. ( http://www.cms.gov/Medicare/Medicare-Fee-for-Service-Payment/sharedsavin...).
    1. Centers for Medicare and Medicaid Services. Medicare shared savings program quality measure benchmarks for the 2014 and 2015 reporting years. ( http://www.cms.gov/Medicare/Medicare-Fee-for-Service-Payment/sharedsavin...).
    1. L&M Policy Research. Evaluation of CMMI accountable care organization initiatives: effect of Pioneer ACOs on Medicare spending in the first year. 2013 Nov 3; ( http://innovation.cms.gov/Files/reports/PioneerACOEvalReport1.pdf).

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