The impacts of accountable care organizations on patient experience,health outcomes and costs: a rapid review

Introduction

Accountable care organizations (ACOs) are groups of physicians, hospitals and other healthcare providers who voluntarily come together to assume collective responsibility for the care of a specific population. ¹ In assuming this responsibility, providers share in any savings or in any potential costs when service delivery and cost are compared to historical benchmarks.

While various models have been operating for some time, ACOs were formally implemented in the US as part of changes made to the Patient Protection and Affordable Care Act in 2012. They have the goal of achieving the ‘Quadruple Aim’ of: (1) improving the patient experience of care, (2) improving population health, (3) reducing the per capita costs of health care and (4) ensuring positive provider experiences. ² To achieve these outcomes, ACOs must create a network of providers (primary-care physicians, specialists, hospitals etc.) to serve a specific patient population; define the population for which the ACO is willing and able to assume risk; ensure the appropriate quality and amount of care is being delivered to those populations and eliminate wasteful expenditure. ³

The ACO model emerged from efforts by both for-profit and not-for-profit insurance companies and Medicare and Medicaid Services to address quality differences and curb increasing healthcare costs. To do so, ACOs are held ‘accountable’ to patients and payers through a pay-for-performance model whereby providers share in the overall savings which are linked, in full or in part, to achieving population-based performance standards on quality measures and to reporting reductions in per member, per month costs.^4,5 This payment model reorients incentives to encourage providers to focus on the total cost of patient care instead of per service payments to provide an incentive for providers to prevent illness. ACOs, however, must ensure that these cost savings are not achieved at the expense of patient care or population health outcomes.

The ACO model has garnered interest among policy-makers in other countries, including England and Canada, to support better management of patients, particularly those with complex needs. ⁶ Policy makers in Ontario, Canada requested this review to inform the province’s ongoing development and implementation of its approach to enhancing the delivery of coordinated care in the community. Our specific objectives were to: (1) identify the impacts of ACOs on improving the quadruple aim goals of improving patient experience of care, enhancing population health outcomes, reducing the per capita cost of health care and ensuring positive provider experiences and (2) determine how and why such impacts have been achieved through ACOs.

Search strategy

We used a rapid review approach, which refers to a streamlined systematic review within a compressed timeline (e.g. to meet policy makers’ needs to inform policy development in a timely way). ⁷ This includes streamlined efforts to identify, organize/map and synthesize findings. ⁸ Our searches therefore focused on identifying potentially relevant systematic reviews and economic evaluations from Health Systems Evidence (www.healthsystemsevidence.org, a repository of systematic reviews addressing health-system topics) and primary studies using a targeted search of PubMed (both were searched from inception to June 2019). In Health Systems Evidence, we searched for ‘accountable care organization’ OR ‘accountable care organizations’ OR ‘accountable care organisation’ OR ‘accountable care organisations’ using the open search. In PubMed, we conducted an open search using the same combination of terms using the ‘health services research’ topic filter for outcomes assessment. We also conducted ‘related articles’ searches in PubMed using two relevant background articles that we identified from preliminary searches of the literature.^9,10 Grey literature was identified by hand searching the CMS (www.cms.gov) and Medicare (www.medicare.gov/) websites and reviewing relevant references from include studies. In addition, two merit reviewers (both of which are from the USA and have extensive knowledge of ACO models) and one of our co-authors who is conversant with the health-policy landscape in the USA provided additional suggestions for relevant literature. Finally, another systematic review has been published since our searches were conducted, which we have also included. ¹¹ We assessed the methodological quality of this systematic review using the AMSTAR tool. ¹² Given that our review was a rapid review of the evidence, we did not conduct quality appraisals of single studies.

The results from the searches were independently assessed for inclusion by two reviewers according to whether the included findings were relevant to our two objectives. One of the authors conducted data extraction, which was checked for consistency by two other authors. For the included studies, we extracted the focus, methods used, description of the sample, jurisdiction(s) studied, key features of the intervention and key findings related to the questions of our review.

Impacts of ACOs

The impacts of the five models of ACOs included in this review on patient experience of care, population health, and per capita cost of health care are summarized in the table in Online Supplement 3. It should be noted that no studies were found that evaluated the quadruple aim in advance payment models on their own, but this model was included in studies that evaluated multiple types of ACOs (Online Supplement 1 references 1,3,5,14,15,20).

How and why the impacts of ACOs have been achieved

We found three qualitative studies, one quantitative survey, and one mixed-methods study relevant to how and why the impacts of ACOs have been achieved. One of the two studies focused on an AQC that incentivized ACOs to meet new paediatric care standards (Online Supplement 1 reference 21). Following the implementation of a paediatric performance-based compensation structure, leaders from 12 of the ACOs involved in the implementation participated in interviews where they reported improvements in the quality of their paediatric care efforts in the form of new practices, metrics and related monitoring (e.g. some started holding meetings to discuss paediatric quality improvement). ACO leaders however, reported that the AQC did little to incentivize the development of paediatric care or the improvement in care for children with specialized needs. The study further indicated that ACO leaders reported that while they implemented attempts to monitor and reduce paediatric spending patterns to align with the incentives offered through the AQC, their attempts did not necessarily change patients’ utilization patterns.

The second study involved interviews with primary-care physicians, administrators executives and who were early adopters of the ACO model. Respondents highlighted mechanisms that enabled the delivery of high-quality primary care, including supplemental staff who assist in care coordination, development of ACO-wide electronic medical records and a higher degree of collaboration and communication among providers in the ACO network (Online Supplement 1 reference 22). However, the study sounded notes of caution relating to the bureaucratic requirements ACOs impose, including referral restrictions, quality monitoring and reporting.

A third study analysed interviews with executives, managers and clinicians at four private sector ACOs to understand how organizational culture change supports the achievement of ACO goals (Online Supplement 1 reference 48). The key cultural shift identified was one from value to volume, which required shifting from organizational and physician accountability to quality outcomes. Challenges to accomplishing this included the ‘open attribution model’ whereby patients may seek care from any provider, despite ACO accountability. Interviewees described using patient engagement and education as well as interdisciplinary and cross-sectoral collaboration to address this challenge. An additional challenge to fostering a value culture was posed by the retrospective nature of claims data, which makes timely evaluation of quality-improvement initiatives difficult.

A fourth study surveyed 33 emergency department directors (26 were directors of ACO-aligned emergency departments) in Massachusetts about strategies used in emergency departments to support ACO objectives (Online Supplement 1 reference 29). Both ACO and non-ACO aligned respondents frequently reported using case management (85% of respondents) and information technology (61%) to reduce costs and admissions. ACO emergency department directors also reported making use of clinical pathways, observation units, and the Medicare three-Day Waiver which allows direct placement into a skilled nursing facility without the standard requirement for a three-day hospital stay. Emergency department directors reported barriers to meeting ACO goals including difficulty coordinating, especially with primary care; physician unfamiliarity with ACO objectives; lack of outcome measurements and lack of financial incentives.

Finally, a mixed-methods study included a thematic analysis of interviews focused on integrating mental health care into primary care in three states (Online Supplement 1 reference 31). Interviewees included state officials, organizational representatives and providers from ACOs as well as from other services supported by State Innovation Model funds. Facilitators to integrating mental health in ACOs and other SIM-supported organizations included tracking mental health quality metrics; integrating mental health in bundled funding; encouraging interprofessional consultation through remote consultation and co-location; fostering informal provider relationships; and developing shared resources including online resource libraries. Barriers included difficulties sharing data between providers given technical and legal constraints, differing professional perspectives between mental health and primary care providers, lack of tailored technical assistance, shortages of mental healthcare providers and differing degrees of implementation across providers.

Principal findings

The reviewed studies suggest that ACOs reduce costs without reducing quality. In addition, while evidence suggests that quality indicators may improve after ACO implementation, changes are often small and metrics such as hospital readmissions or care for specific disorders may not be affected. Cost savings were largely attributable to savings in outpatient expenses among the most medically complex patients and to reductions of low-value services. Cost savings across the ACO models were modest, notably for PGPs and MSSPs, which in many cases did not produce enough savings to receive bonuses. Most ACO models were found to meet the majority of the quality measures and performed better than their fee-for-service counterpart. It remains uncertain, however, whether these metrics are adequately measuring the quality of care, as reported in one study. ¹⁴ Finally, relatively little evidence was found for the impact of ACOs on provider experience, limiting the extent to which any conclusions could be drawn.

Implications for policy

Since the passage of the Affordable Care Act, the US health care industry has seen a rapid growth in new funding models to improve experiential and health outcomes and reduce per capita spending. Chief among these new funding models are ACOs that number in excess of 700 functioning in the commercial, Medicare and Medicaid markets. ¹⁵ While ACOs have a defining architecture (networks of providers held accountable to payers for cost and quality for a defined population), ¹⁶ they differ substantially in their geographies and target populations, provider composition (e.g. mix of independent physician practices, hospitals and other organizations), financial models (e.g. mix of upside gain sharing vs. downside financial risk), and cost avoidance and quality enhancement strategies (e.g. care management models for high risk persons, adoption of predictive analytics, care transition planning or shared decision-making). ¹⁶ With their substantial heterogeneity in approaches to financing and delivering healthcare, our findings that ACO impacts are mixed is both encouraging and expected. The findings suggest that quadruple–aim improvements are possible with ACO models. However, while some rigorous evaluations are available, particularly for the MSSP and Pioneer models, more clarity is needed on how ACOs differ in their success based on their organizational characteristics, target populations, risk and gain-sharing strategies and clinical interventions. As findings continue to emerge from these experiences, US policy makers will require more synthesized evidence such as this to adjust their ACO strategies based on the emerging literature.

These findings are also relevant to policy makers in other countries who face similar challenges in making their systems more effective and efficient through various accountability structures, payment mechanisms and care-integration strategies. As scale, pace and heterogeneity of the US ACO innovations dwarf the magnitude of those in other nations, policy makers should consider what lessons can be learnt from the implementation of ACOs in the USA, bearing in mind that the US healthcare context can differ significantly from that of other countries.

Implications for research

Several implications for research can be drawn from our review. First, the literature suggests there is consensus around the call for continued research and continued monitoring of indicators (including continuous monitoring of costs, their rate of growth and how savings are being produced) because of the mixed results from early analysis or because ACOs have had too short a track record to evaluate effects on quality of care and costs. Second, the limited number of studies directly assessing ACOs’ population health outcomes points to the need for enhanced measurement and continuous evaluation in this specific area. ² Lastly, the lack of research evidence about how and why impacts are achieved in ACOs points to the need for further process evaluations (e.g. by interviewing leaders about what they found to be the essential components for success, as well as what factors acted as barriers to implementation).

Strengths and limitations

The main strengths of this review are that it provides synthesized evidence about an important system-level intervention and that it complements an existing systematic review that provides findings related to utilization and process-related outcomes. However, there are some limitations to our study, which primarily relate to this review being conducted in a compressed time frame. First, while a comprehensive search was conducted in two databases, there was insufficient time to search other databases, to ensure comprehensiveness. Second, no quality appraisal was conducted for primary studies – although making such methodological trade-offs is consistent with the time-limited approach taken in other rapid review methodologies.^17,18 In relation to quality, a number of the studies included in this review, particularly those that examined patient engagement, used self-reported data and may be subject to response bias. Third, a lack of available data to address each question or all three of the Quadruple-Aim outcomes limits the reliability of findings; however, this highlights a need for continued monitoring of indicators and further research to assess impacts.