The one-year impact of accountable care networks among Washington State employees.

OBJECTIVE: To estimate the impact of a new, two-sided risk model accountable care network (ACN) on Washington State employees and their families. DATA SOURCES/STUDY SETTING: Administrative data (January 2013-December 2016) on Washington State employees. STUDY DESIGN: We compared monthly health care utilization, health care intensity as measured through proxy pricing, and annual HEDIS quality metrics between the five intervention counties to 13 comparison counties, analyzed separately by age categories (ages 0-5, 6-18, 19-26, 18-64). DATA COLLECTION/EXTRACTION METHODS: We used difference-in-difference methods and generalized estimating equations to estimate the effects after 1 year of implementation for adults and children. PRINCIPAL FINDINGS: We estimate a 1-2 percentage point decrease in outpatient hospital visits due to the introduction of ACNs (adults: -1.8, P < .01; age 0-5: -1.2, P = .07; age 6-18: -1.2, P = .06; age 19-26; -1.2, P < .01). We find changes in primary and specialty care office visits; the direction of impact varies by age. Dependents age 19-26 were also responsive with inpatient admissions declines (-0.08 percentage points, P = .02). Despite changes in utilization, there was no evidence of changes in intensity of care and mixed results in the quality measures. CONCLUSIONS: Washington's state employee ACN introduction changed health care utilization patterns in the first year but was not as successful in improving quality.

Accountable Care Organizations during Covid-19: Routine care for older adults with multiple chronic conditions.

The COVID-19 pandemic threatens the health and well-being of older adults with multiple chronic conditions. To date, limited information exists about how Accountable Care Organizations (ACOs) are adapting to manage these patients. We surveyed 78 Medicare ACOs about their concerns for these patients during the pandemic and strategies they are employing to address them. ACOs expressed major concerns about disruptions to necessary care for this population, including the accessibility of social services and long-term care services. While certain strategies like virtual primary and specialty care visits were being used by nearly all ACOs, other services such as virtual social services, home medication delivery, and remote lab monitoring were far less commonly accessible. ACOs expressed that support for telehealth services, investment in remote monitoring capabilities, and funding for new, targeted care innovation initiatives would help them better care for vulnerable patients during this pandemic.

Proportion of Racial Minority Patients and Patients With Low Socioeconomic Status Cared for by Physician Groups After Joining Accountable Care Organizations.

Importance: The incentive structure of accountable care organizations (ACOs) may lead to participating physician groups selecting fewer vulnerable patients. Objective: To test for changes in the percentage of racial minority patients and patients with low socioeconomic status cared for by physician groups after joining the ACO. Design, Setting, and Participants: This retrospective cohort consisted of a 15% random sample of Medicare fee-for-service beneficiaries attributed to physician groups from 2010 to 2016. Medicare Shared Savings Program (MSSP) participation was determined using ACO files. Analyses were conducted between January 1, 2019, and February 25, 2020. Exposures: Using linear probability models, we conducted difference-in-differences analyses based on the year a physician group joined an ACO to estimate changes in vulnerable patients within ACO-participating groups compared with nonparticipating groups. Main Outcomes and Measures: Whether the patient was black, was dually enrolled in Medicare and Medicaid, and poverty and unemployment rates of the patient's zip code. Results: In a cohort of 76 717 physician groups caring for 7 307 130 patients, 16.1% of groups caring for 27.8% of patients participated in an MSSP ACO. Using 2010 characteristics, patients attributed to ACOs from 2012 to 2016, compared with those who were not, were less likely to be black (8.0% [n = 81 698] vs 9.3% [n = 270 924]) or dually enrolled in Medicare and Medicaid (12.8% [n = 130 957] vs 18.2% [n = 528 685]), and lived in zip codes with lower poverty rates (13.8% vs 15.5%); unemployment rates were similar (8.0% vs 8.5%). In the difference-in-differences analysis, there was no statistically significant change associated with ACO participation in the proportions of vulnerable patients attributed to ACO-participating groups compared with nonparticipating groups. After joining an ACO, ACO-participating groups had 0.0 percentage points change (95% CI, -0.1 to 0.1 percentage points; P = .59) for black patients, -0.1 percentage points (95% CI, -0.2 to 0.1 percentage points; P = .32) for patients dually enrolled in Medicare and Medicaid, 0.2 percentage points (95% CI, -3.5 to 4.0 percentage points; P = .91) in poverty rates, and -0.4 percentage points (95% CI, -2.0 to 1.2 percentage points; P = .62) in unemployment rates. Conclusions and Relevance: In this cohort study, there were no changes in the proportions of vulnerable patients cared for by ACO-participating physician groups after joining an ACO compared with changes among nonparticipating groups.

Development and evaluation of physician-precepted advanced pharmacy practice experiences (APPEs) within an accountable care organization (ACO).

BACKGROUND AND PURPOSE: The American Council of Pharmaceutical Education (ACPE) standards emphasize that pharmacy graduates should be "practice- and team-ready," and the American Society for Health-System Pharmacists (ASHP) Task Force on accountable care organizations (ACOs) states that curricula at pharmacy schools should be evaluated and reworked to prepare students to practice effectively as members of the health care team within ACOs. The objective of this study was to describe the development of an ACO-based advanced pharmacy practice experience (APPE) rotation block, clinical activities and interventions completed by students during the experience, and perceptions of students, patients, and physician preceptors regarding the experience. EDUCATIONAL ACTIVITY AND SETTING: The rotation block was within outpatient ACO offices and consisted of a four-week rotation with one pharmacy faculty, immediately followed by a four-week elective experience in a different office with a physician serving as primary preceptor. FINDINGS: Eight students completed the rotation block between August 2017 and April 2018. Students documented a total of 1299 clinical activities and 65 interventions. Medication reconciliation and recommendations to initiate a medication were the most commonly completed activities and interventions documented. The experience was positively perceived among surveyed students, patients, and physician preceptors. SUMMARY: The rotation block was successfully implemented with a positive response from students, patients, and physician preceptors. As a result, the program has expanded in accordance with ACPE Standards to create "practice- and team-readiness" among graduates and expose students to interdisciplinary care within ACOs and other settings.

Putting the puzzle pieces together: Adapting a population health infrastructure to Medicaid risk.

As Accountable Care Organizations (ACOs) become more common within state Medicaid programs, health systems are increasingly facing the challenge of developing a population health approach for this population. This case report considers how health systems with a mature population health infrastructure evolve, adapt, and expand programs to take on Medicaid risk and better serve the Medicaid population. Four key implementation lessons were garnered from Partners HealthCare's experience that may be relevant for organizations undergoing similar transformations: 1) A significant portion of a health system's existing population health strategy can be applied to the Medicaid risk population; 2) Leveraging existing population health infrastructure can assist in adapting and adding programs; 3) Additional attention needs to be paid to behavioral health, substance use, and social determinants of health needs across existing and new programing; 4) Patients need to be engaged outside of the traditional primary care setting, including in the emergency department, and through home and community based care.

Out of Physicians' Hands: TMA Challenges Unfair Quality Measures on Medication Adherence.

Only patients can pick up their own prescriptions, and only patients can propel that medication into their own bodies. Physicians can educate, emphasize, and admonish - but at the end of the day, they can't restrain and "pill" a squirming, uncooperative patient like a dog or cat. It's up to patients to do the right thing for themselves. Yet, some health plans' quality programs are putting that onus on physicians - through medication adherence metrics that determine whether physicians and accountable care organizations (ACOs) in value-based contracts receive bonus payments.

How does being part of a pediatric accountable care organization impact health service use for children with disabilities?

OBJECTIVE: To examine the impact of a Medicaid-serving pediatric accountable care organization (ACO) on health service use by children who qualify for Medicaid by virtue of a disability under the "aged, blind, and disabled" (ABD) eligibility criteria. DATA SOURCES/STUDY SETTING: We evaluated a 2013 Ohio policy change that effectively moved ABD Medicaid children into an ACO model of care using Ohio Medicaid administrative claims data for years 2011-2016. STUDY DESIGN: We used a difference-in-difference design to examine changes in patterns of health care service use by ABD-enrolled children before and after enrolling in an ACO compared with ABD-enrolled children enrolled in non-ACO managed care plans. DATA COLLECTION/EXTRACTION METHODS: We identified 17 356 children who resided in 34 of 88 counties as the ACO "intervention" group and 47 026 ABD-enrolled children who resided outside of the ACO region as non-ACO controls. PRINCIPAL FINDINGS: Being part of the ACO increased adolescent preventative service and decreased use of ADHD medications as compared to similar children in non-ACO capitated managed care plans. Relative home health service use decreased for children in the ACO. CONCLUSIONS: Our overall results indicate that being part of an ACO may improve quality in certain areas, such as adolescent well-child visits, though there may be room for improvement in other areas considered important by patients and their families such as home health service.

Optimizing the Role of Community Pharmacists in Managing the Health of Populations: Barriers, Facilitators, and Policy Recommendations.

The shift to a value-based health care system has incentivized providers to implement strategies that improve population health outcomes while minimizing downstream costs. Given their accessibility and expanded clinical care models, community pharmacists are well positioned to join interdisciplinary care teams to advance efforts in effectively managing the health of populations. In this Viewpoints article, we discuss the expanded role of community pharmacists and potential barriers limiting the uptake of these services. We then explore strategies to integrate, leverage, and sustain these services in a value-based economy. Although community pharmacists have great potential to improve population health outcomes because of their accessibility and clinical interventions that have demonstrated improved outcomes, pharmacists are not recognized as merit-based incentive eligible providers and, as a result, may be underutilized in this role. Additional barriers include lack of formal billing codes, which limits patient access to services such as hormonal contraception; fragmentation of Medicare, which prevents alignment of medical and pharmaceutical costs; and continued fee-for-service payment models, which do not incentivize quality. Despite these barriers, there are several opportunities for continued pharmacist involvement in new care models such as patient-centered medical homes (PCMH), accountable care organizations, and other value-based payment models. Community pharmacists integrated within PCMHs have demonstrated improved hemoglobin A1c, blood pressure control, and immunization rates. Likewise, other integrated, value-based models that used community pharmacists to provide medication therapy management services have reported a positive return on investment in overall health care costs. To uphold these efforts and effectively leverage community pharmacist services, we recommend the following: (a) recognition of pharmacists as providers to facilitate full participation in performance-based models, (b) increased integration of pharmacists in emerging delivery and payment models with rapid cycle testing to further clarify the role and value of pharmacists, and (c) enhanced collaborative relationships between pharmacists and other providers to improve interdisciplinary care. DISCLOSURES: This article was funded by the National Association of Chain Drug Stores. The authors have no potential conflicts of interest to report.

Performance in the Medicare Shared Savings Program After Accounting for Nonrandom Exit: An Instrumental Variable Analysis.

Background: Accountable care organizations (ACOs) in the Medicare Shared Savings Program (MSSP) are associated with modest savings. However, prior research may overstate this effect if high-cost clinicians exit ACOs. Objective: To evaluate the effect of the MSSP on spending and quality while accounting for clinicians' nonrandom exit. Design: Similar to prior MSSP analyses, this study compared MSSP ACO participants versus control beneficiaries using adjusted longitudinal models that accounted for secular trends, market factors, and beneficiary characteristics. To further account for selection effects, the share of nearby clinicians in the MSSP was used as an instrumental variable. Hip fracture served as a falsification outcome. The authors also tested for compositional changes among MSSP participants. Setting: Fee-for-service Medicare, 2008 through 2014. Patients: A 20% sample (97 204 192 beneficiary-quarters). Measurements: Total spending, 4 quality indicators, and hospitalization for hip fracture. Results: In adjusted longitudinal models, the MSSP was associated with spending reductions (change, -$118 [95% CI, -$151 to -$85] per beneficiary-quarter) and improvements in all 4 quality indicators. In instrumental variable models, the MSSP was not associated with spending (change, $5 [CI, -$51 to $62] per beneficiary-quarter) or quality. In falsification tests, the MSSP was associated with hip fracture in the adjusted model (-0.24 hospitalizations for hip fracture [CI, -0.32 to -0.16 hospitalizations] per 1000 beneficiary-quarters) but not in the instrumental variable model (0.05 hospitalizations [CI, -0.10 to 0.20 hospitalizations] per 1000 beneficiary-quarters). Compositional changes were driven by high-cost clinicians exiting ACOs: High-cost clinicians (99th percentile) had a 30.4% chance of exiting the MSSP, compared with a 13.8% chance among median-cost clinicians (50th percentile). Limitation: The study used an observational design and administrative data. Conclusion: After adjustment for clinicians' nonrandom exit, the MSSP was not associated with improvements in spending or quality. Selection effects-including exit of high-cost clinicians-may drive estimates of savings in the MSSP. Primary Funding Source: Horowitz Foundation for Social Policy, Agency for Healthcare Research and Quality, and National Institute on Aging.

Accountable Care Organizations' Performance in Depression: Lessons for Value-Based Payment and Behavioral Health.

Value-based payment initiatives, such as the Medicare Shared Savings Program (MSSP), offer the possibility of using financial incentives to drive improvements in mental health and substance use outcomes. In the past 2 years, Accountable Care Organizations (ACOs) participating in the MSSP began to publicly report on one behavioral health outcome-Depression Remission at Twelve Months, which may indicate how value-based payment incentives have impacted mental health and substance use, and if reforms are needed. For ACOs that meaningfully reported performance on the depression remission measure in 2017, the median rate of depression remission at 12 months was 8.33%. A recent meta-analysis found that the average rate of spontaneous depression remission at 12 months absent treatment was approximately 53%. Although a number of factors likely explain these results, the current ACO design does not appear to incentivize improved behavioral health outcomes. Four changes in value-based payment incentive design may help to drive better outcomes: (1) making data collection easier, (2) increasing the salience of incentives, (3) building capacity to implement new interventions, and (4) creating safeguards for inappropriate treatment or reporting.

Recommended Cancer Screening in Accountable Care Organizations: Trends in Colonoscopy and Mammography in the Medicare Shared Savings Program.

PURPOSE: Accountable care organizations (ACOs) are a delivery and payment model designed to encourage integrated, high-value care. We designed a study to test the association between ACOs and two recommended cancer screening tests, colonoscopy for colorectal cancer and mammography for breast cancer. METHODS: Using the random 20% sample of Medicare claims, beneficiaries were attributed to ACO or non-ACO cohorts on the basis of providers' enrollment in the Medicare Shared Savings Program. An inverse probability of treatment weighting was used to balance patient characteristics between ACO and non-ACO cohorts. A propensity score-weighted, difference-in-differences analysis was then performed using the same provider groups in 2010-pre-ACO-as a baseline. A secondary analysis for older-nonrecommended-age ranges was performed. RESULTS: Prevalence of colonoscopy in recommended age ranges in ACOs from 2010 to 2014 increased from 15.3% (95% CI, 14.9% to 15.6%) to 17.9% (95% CI, 17.3% to 18.5%). This differed significantly from the change in non-ACOs (difference in differences, 1.2%; P < .001). Among women in ACOs, mammography prevalence rose from 53.7% (95% CI, 53.0% to 54.4%) to 54.9% (95% CI, 54.2% to 55.7%). In contrast to colonoscopy, the difference in mammography prevalence was not significantly different in ACO versus non-ACOs (difference in differences, 0.49%; P < .13). A similar pattern was also observed in older-nonrecommended-age ranges with significant difference in differences (ACO v non-ACO) in colonoscopy, but not mammography. CONCLUSION: The impact of ACOs on cancer screening varies between screening tests. Our results are consistent with a greater effect of ACOs on high-cost, high-complexity screening services, which may be more sensitive to integrated care delivery models.

The impact of accountable care organization participation on hospital patient experience.

BACKGROUND: Accountable care organizations (ACOs) are being implemented rapidly across the Unites States. Previous studies indicated an increasing number of hospitals have participated in ACOs. However, little is known about how ACO participation could influence hospitals' performance. PURPOSE: This study aims to examine the impact of Medicare ACO participation on hospitals' patient experience. METHODOLOGY/APPROACH: Difference-in-difference analyses were conducted to compare 10 patient experience measures between hospitals participating in Medicare ACOs and those not participating. RESULTS: In general, hospitals participating in Pioneer ACOs had significantly improved scores on nursing communication and doctor communication. Shared Savings Program (SSP) ACO participation did not show significant improvement of patient experience. Subgroup analyses indicate that, for hospitals in the middle and top tertile groups in terms of baseline experience, Pioneer ACO and SSP ACO participation was associated with better patient experience. For hospitals in the bottom tertile, Pioneer ACO and SSP ACO participation had no association with patient experience. CONCLUSION: ACO participation improved some aspects of patient experience among hospitals with prior good performance. However, hospitals with historically poor performance did not benefit from ACO participation. PRACTICE IMPLICATIONS: Prior care coordination and quality improvement experience position Medicare ACOs for greater success in terms of patient experience. Hospital leaders need to consider the potential negative consequences of ACO participation and the hospital's preparedness for care coordination.

Admission diagnoses among patients with heart failure: Variation by ACO performance on a measure of risk-standardized acute admission rates.

BACKGROUND: A key quality metric for Accountable Care Organizations (ACOs) is the rate of hospitalization among patients with heart failure (HF). Among this patient population, non-HF-related hospitalizations account for a substantial proportion of admissions. Understanding the types of admissions and the distribution of admission types across ACOs of varying performance may provide important insights for lowering admission rates. METHODS: We examined admission diagnoses among 220 Medicare Shared Savings Program ACOs in 2013. ACOs were stratified into quartiles by their performance on a measure of unplanned risk-standardized acute admission rates (RSAARs) among patients with HF. Using a previously validated algorithm, we categorized admissions by principal discharge diagnosis into: HF, cardiovascular/non-HF, and noncardiovascular. We compared the mean admission rates by admission type as well as the proportion of admission types across RSAAR quartiles (Q1-Q4). RESULTS: Among 220 ACOs caring for 227,356 patients with HF, the median (IQR) RSAARs per 100 person-years ranged from 64.5 (61.7-67.7) in Q1 (best performers) to 94.0 (90.1-99.9) in Q4 (worst performers). The mean admission rates by admission types for ACOs in Q1 compared with Q4 were as follows: HF admissions: 9.8 (2.2) vs 14.6 (2.8) per 100 person years (P < .0001); cardiovascular/non-HF admissions: 11.1 (1.6) vs 15.9 (2.6) per 100 person-years (P < .0001); and noncardiovascular admissions: 42.7 (5.4) vs 69.6 (11.3) per 100 person-years (P < .0001). The proportion of admission due to HF, cardiovascular/non-HF, and noncardiovascular conditions was 15.4%, 17.5%, and 67.1% in Q1 compared with 14.6%, 15.9%, and 69.4% in Q4 (P < .007). CONCLUSIONS: Although ACOs with the best performance on a measure of all-cause admission rates among people with HF tended to have fewer admissions for HF, cardiovascular/non-HF, and noncardiovascular conditions compared with ACOs with the worst performance (highest admission rates), the largest difference in admission rates were for noncardiovascular admission types. Across all ACOs, two-thirds of admissions of patients with HF were for noncardiovascular causes. These findings suggest that comprehensive approaches are needed to reduce the diverse admission types for which HF patients are at risk.

The role of accountable care organization affiliation and ownership in promoting physician practice participation in quality improvement collaboratives.

BACKGROUND: Quality improvement collaboratives (QICs) have emerged as an important strategy to improve processes and outcomes of clinical care through interorganizational learning. Little is known about the organizational factors that support or deter physician practice participation in QICs. PURPOSE: The aim of this study was to examine organizational influences on physician practices' propensity to participate in QICs. We hypothesized that practice affiliation with an accountable care organization (ACO) and practice ownership by a system or community health center (CHC) would increase the propensity of physician practices to participate in a QIC. METHODOLOGY: Data from the third wave of the National Study of Physician Organizations, a nationally representative sample of medical practices (n = 1,359), were analyzed. Weighted multivariate regression analyses were estimated to examine the association of ACO affiliation, ownership, and QIC participation, controlling for practice size, health information technology capacity, public reporting participation, and practice revenue from Medicaid and uninsured patients. The Sobel-Goodman Test was used to explore the extent to which practice use of quality improvement (QI) methods such as Lean, Six Sigma, and use of plan-do-study-act cycles mediates the relationship between ACO affiliation and QIC participation. FINDINGS: Only 13.6% of practices surveyed in 2012-2013 participated in a QIC. In adjusted analyses, ACO affiliation (odds ratio [OR] = 1.51, p < .01), CHC ownership (OR = 6.57, p < .001), larger practice size (OR = 14.72, p < .001), and health information technology functionality (OR = 1.15, p < .001) were positively associated with QIC participation. Practice use of QI methods partially mediated (13.1%-46.7%) the association of ACO affiliation with QIC participation. PRACTICE IMPLICATIONS: ACO-affiliated practices are more likely than non-ACO practices to participate in QICs. Practice size rather than system ownership appears to influence QIC participation. QI methods often promoted and used by health care systems such as CHCs and ACOs may promote QIC participation.

Alterations in 90-day morbidity, mortality, and readmission rates following spine surgery in Medicare Accountable Care Organizations (2009-2014).

BACKGROUND CONTEXT: The impact of Accountable Care Organizations (ACOs) on healthcare quality and outcomes, including morbidity, mortality, and readmissions, has not been substantially investigated, especially following spine surgery. PURPOSE: To evaluate the impact of ACO formation on postoperative outcomes in the 90-day period following spine surgery. STUDY DESIGN: Retrospective review of national Medicare claims data (2009-2014). PATIENT SAMPLE: Patients who underwent one of four lumbar spine surgical procedures in an ACO or non-ACO. OUTCOME MEASURES: The development of in-hospital mortality, complications or hospital readmission within 90 days of the surgical procedure. METHODS: The primary outcome measures included postsurgical complications and readmissions at 90 days following surgery. In-hospital mortality and 30-day outcomes were considered secondarily. The primary predictor variable consisted of ACO enrollment designation. Multivariable logistic regression analysis was utilized to adjust for confounders and determine the independent effect of ACO enrollment on postsurgical outcomes. The multivariable model included a propensity score adjustment that accounted for factors associated with the preferential enrollment of patients in ACOs, namely, sociodemographic characteristics, medical co-morbidities, hospital teaching status, bed size, and location. RESULTS: In all, there were 344,813 patients identified for inclusion in this analysis with 97% (n = 332,890) treated in non-ACOs and 3% (n = 11,923) in an ACO. Although modest changes were apparent across both ACOs and non-ACOs over the time-period studied, improvements were slightly more dramatic in non-ACOs leading to statistically significant differences in both 90-day complications and readmissions. Specifically, in the period 2012-2014, ACOs demonstrated an 18% increase in the odds of 90-day complications and a 14% elevation in the odds of 90-day readmissions when compared to non-ACOs. There was no difference in hospital mortality between ACOs and non-ACOs. CONCLUSIONS: Our study of Medicare data from 2009 to 2014 failed to demonstrate superior reductions in postoperative morbidity, mortality, and readmissions for beneficiaries treated in ACOs as compared to non-ACOs. These results indicate that meaningful changes in postoperative outcomes should not be anticipated based on organizational participation in ACOs at present.

The Accountable Care Organization for Surgical Care.

Rising health care costs superimposed on uncertainty surrounding the relationship between health care spending and quality have resulted in an urgent need to develop strategies to better align health care payment with value. Such approaches, at least in theory, work to achieve the dual aims of reducing growth in health care spending and improving population health. To date, surgery has not been prioritized in accountable care organizations (ACOs). Nonetheless, it is critically important to begin to consider strategic and impactful mechanisms through which surgery can be seamlessly woven into innovative population health models.

ACOs' Impact on Hospitalization Rates of Rural Older Adults With Diabetes: Early Indications.

The purpose of this study was to examine the impact of Medicare Shared Savings Program Accountable Care Organizations (SSP ACOs), along with other factors, on diabetes-related hospitalization rates for rural older adults. Using an early year of the SSP ACO program, we conducted multiple linear regressions to examine the effect of ACO participation on African American and white older adults. In neither model was ACO affiliation found to have a statistically significant impact on diabetes-related hospitalization rates. This study provides baseline measures for patient outcomes during the initial years of ACO formation.

Comparison of Approaches for Aggregating Quality Measures in Population-based Payment Models.

OBJECTIVE: To assess the impact of alternative methods of aggregating individual quality measures on Accountable Care Organization (ACO) overall scores. DATA SOURCE: 2014 quality scores for Medicare ACOs. STUDY DESIGN: We compare ACO overall scores derived using CMS' aggregation approach to those derived using alternative approaches to grouping and weighting measures. PRINCIPAL FINDINGS: Alternative grouping and weighting methods based on statistical criteria produced overall quality scores similar to those produced using CMS' approach (κ = 0.80 to 0.95). Scores derived from giving specific domains greater weight were less similar (κ = 0.51 to 0.93). CONCLUSIONS: How measures are grouped into domains and how these domains are weighted to generate overall scores can have important implications for ACO's shared savings payments.