Opportunities for Savings in Risk Arrangements for Oncologic Care.

Importance: As the US accelerates adoption of alternative payment through global payment models such as Accountable Care Organizations (ACOs) or Medicare Advantage (MA), high spending for cancer care is a potential target for savings. Objective: To quantify the extent to which ACOs and other risk-bearing organizations operating in a specific geographic area (hospital referral region [HRR]) could achieve savings by steering patients to efficient medical oncology practices. Design, Setting, and Participants: This observational study included serial cross-sections of Medicare beneficiaries with cancer from 2010 to 2018. Data were analyzed from August 2021 to March 2023. Main Outcomes and Measures: Total spending and spending by category in the 1-year period following an index visit for a patient with newly diagnosed (incident) or poor-prognosis cancer. Results: The incident cohort included 1 309 825 patients with a mean age of 74.0 years; the most common cancer types were breast (21.4%), lung (16.7%), and colorectal cancer (10.0%). The poor prognosis cohort included 1 429 973 (mean age, 72.7 years); the most common cancer types were lung (26.6%), lymphoma (11.7%), and leukemia (7.3%). Options for steering varied across markets; the top quartile market had 10 or more oncology practices, but the bottom quartile had 3 or fewer oncology practices. Total spending (including Medicare Part D) in the incident cohort increased from a mean of $57 314 in 2009 to 2010 to $66 028 in 2016 to 2017. Within markets, total spending for practices in the highest spending quartile was 19% higher than in the lowest quartile. Hospital spending was the single largest component of spending in both time periods ($20 390 and $19 718, respectively) followed by Part B (infused) chemotherapy ($8022 and $11 699). Correlations in practice-level spending between the first-year (2009) and second-year (2010) spending were high (>0.90 in all categories with most >0.98), but these attenuated over time. Conclusions and Relevance: These results suggest there may be opportunities for ACOs and other risk-bearing organizations to select or drive referrals to lower-spending oncology practices in many local markets.

Discharge prescribing and subsequent opioid use after traumatic musculoskeletal injury.

OBJECTIVE: To investigate the effects of discharge opioid supply after surgery for musculoskeletal injury on subsequent opioid use. STUDY DESIGN: Instrumental variables analysis of retrospective administrative data. METHODS: Data were acquired on 1039 patients treated operatively for a musculoskeletal injury between 2011 and 2015 at 2 level I trauma centers. State registry data were used to track all postoperative opioid prescription fills. Discharge surgical resident was identified for each patient. We categorized residents in the top one-third of opioid prescribing as high-supply residents and others as low-supply residents, with adjustment for service attending physician and month. The primary outcome was subsequent opioid use, defined as new opioid prescriptions and cumulative prescribed opioid supply 7 to 8 months after injury. RESULTS: On average, patients of high-supply residents received an additional 96 morphine milligram equivalents (MME) at discharge (95% CI, 29-163 MME; P < .01), or 16% more, compared with patients of low-supply residents, which is equivalent to an additional 2-day supply at a typical dosage. In the seventh or eighth month after surgery, patients of high-supply residents received a greater total MME volume than patients of low-supply residents (difference, 13.0 MME; 95% CI, 3.1-22.9 MME; P < .01) despite receiving a greater cumulative supply of opioid medications through the sixth month after surgery. CONCLUSIONS: After surgery for musculoskeletal injury, patients discharged by residents who prescribe greater supplies of opioid pain medications received higher supplies of opioids 7 to 8 months after surgery than patients discharged by residents who tend to prescribe less. Thus, limiting postoperative supplies of opioid pain medication may help reduce chronic opioid use.

Association of Functional Status, Cognition, Social Support, and Geriatric Syndrome With Admission From the Emergency Department.

Importance: The role of patient-level factors that are unrelated to the specific clinical condition leading to an emergency department (ED) visit, such as functional status, cognitive status, social supports, and geriatric syndromes, in admission decisions is not well understood, partly because these data are not available in administrative databases. Objective: To determine the extent to which patient-level factors are associated with rates of hospital admission from the ED. Design, Setting, and Participants: This cohort study analyzed survey data collected from participants (or their proxies, such as family members) enrolled in the Health and Retirement Study (HRS) from January 1, 2000, to December 31, 2018. These HRS data were linked to Medicare fee-for-service claims data from January 1, 1999, to December 31, 2018. Information on functional status, cognitive status, social supports, and geriatric syndromes was obtained from the HRS data, whereas ED visits, subsequent hospital admission or ED discharge, and other claims-derived comorbidities and sociodemographic characteristics were obtained from Medicare data. Data were analyzed from September 2021 to April 2023. Main Outcomes and Measures: The primary outcome measure was hospital admission after an ED visit. A baseline logistic regression model was estimated, with a binary indicator of admission as the dependent variable of interest. For each primary variable of interest derived from the HRS data, the model was reestimated, including the HRS variable of interest as an independent variable. For each of these models, the odds ratio (OR) and average marginal effect (AME) of changing the value of the variable of interest were calculated. Results: A total of 42 392 ED visits by 11 783 unique patients were included. At the time of the ED visit, patients had a mean (SD) age of 77.4 (9.6) years, and visits were predominantly for female (25 719 visits [60.7%]) and White (32 148 visits [75.8%]) individuals. The overall percentage of patients admitted was 42.5%. After controlling for ED diagnosis and demographic characteristics, functional status, cognition status, and social supports all were associated with the likelihood of admission. For instance, difficulty performing 5 activities of daily living was associated with an 8.5-percentage point (OR, 1.47; 95% CI, 1.29-1.66) AME increase in the likelihood of admission. Having dementia was associated with an AME increase in the likelihood of admission of 4.6 percentage points (OR, 1.23; 95% CI, 1.14-1.33). Living with a spouse was associated with an AME decrease in the likelihood of admission of 3.9 percentage points (OR, 0.84; 95% CI, 0.79-0.89), and having children living within 10 miles was associated with an AME decrease in the likelihood of admission of 5.0 percentage points (OR, 0.80; 95% CI, 0.71-0.89). Other common geriatric syndromes, including trouble falling asleep, waking early, trouble with vision, glaucoma or cataract, use of hearing aids or trouble with hearing, falls in past 2 years, incontinence, depression, and polypharmacy, were not meaningfully associated with the likelihood of admission. Conclusion and Relevance: Results of this cohort study suggest that the key patient-level characteristics, including social supports, cognitive status, and functional status, were associated with the decision to admit older patients to the hospital from the ED. These factors are critical to consider when devising strategies to reduce low-value admissions among older adult patients from the ED.

Benchmarking Changes And Selective Participation In The Medicare Shared Savings Program.

In 2017 the Medicare Shared Savings Program (MSSP) began incorporating regional spending into accountable care organization (ACO) benchmarks, thus favoring the participation of ACOs and practices with lower baseline spending than their region. To characterize providers' responses to these incentives, we isolated changes in spending due to changes in the mix of ACOs and practices participating in the MSSP. In contrast to earlier participation patterns, the composition of the MSSP after 2017 increasingly shifted to providers with lower preexisting levels of spending relative to their region, consistent with a selection response. Changes occurred through the entry of new ACOs with lower baseline spending, the exit of higher-spending ACOs, and the reconfiguration of participant lists favoring lower-spending practices within continuing ACOs. These participation patterns varied meaningfully by ACO type. Although compositional changes could not be definitively tied to benchmarking changes, the disproportionate participation of providers with lower baseline spending implies substantial costs and the need for ACO benchmarking reforms.

Racial and Ethnic Disparities in Health Care Use and Access Associated With Loss of Medicaid Supplemental Insurance Eligibility Above the Federal Poverty Level.

Importance: Medicaid supplemental insurance covers most cost sharing in Medicare. Among low-income Medicare beneficiaries, the loss of Medicaid eligibility above this program's income eligibility threshold (100% of federal poverty level [FPL]) may exacerbate racial and ethnic disparities in Medicare beneficiaries' ability to afford care. Objective: To examine whether exceeding the income threshold for Medicaid, which results in an abrupt loss of Medicaid eligibility, is associated with greater racial and ethnic disparities in access to and use of care. Design, Setting, and Participants: This cross-sectional study used a regression discontinuity design to assess differences in access to and use of care associated with exceeding the income threshold for Medicaid eligibility. We analyzed Medicare beneficiaries with incomes 0% to 200% of FPL from the 2008 to 2018 biennial waves of the Health and Retirement Study linked to Medicare administrative data. To identify racial and ethnic disparities associated with the loss of Medicaid eligibility, we compared discontinuities in outcomes among Black and Hispanic beneficiaries (n = 2885) and White beneficiaries (n = 5259). Analyses were conducted between January 1, 2022, and October 1, 2022. Main outcome measures: Patient-reported difficulty accessing care due to cost and outpatient service use, medication fills, and hospitalizations measured from Medicare administrative data. Results: This cross-sectional study included 8144 participants (38 805 person-years), who when weighted represented 151 282 957 person-years in the community-dwelling population of Medicare beneficiaries aged 50 years and older and incomes less than 200% FPL. In the weighted sample, the mean (SD) age was 75.4 (9.4) years, 66.1% of beneficiaries were women, 14.8% were non-Hispanic Black, 13.6% were Hispanic, and 71.6% were White. Findings suggest that exceeding the Medicaid eligibility threshold was associated with a 43.8 percentage point (pp) (95% CI, 37.8-49.8) lower probability of Medicaid enrollment among Black and Hispanic Medicare beneficiaries and a 31.0 pp (95% CI, 25.4-36.6) lower probability of Medicaid enrollment among White beneficiaries. Among Black and Hispanic beneficiaries, exceeding the threshold was associated with increased cost-related barriers to care (discontinuity: 5.7 pp; 95% CI, 2.0-9.4), lower outpatient use (-6.3 services per person-year; 95% CI, -10.4 to -2.2), and fewer medication fills (-6.9 fills per person-year; 95% CI, -11.4 to -2.5), but it was not associated with a statistically significant discontinuity in hospitalizations. Discontinuities in these outcomes were smaller or nonsignificant among White beneficiaries. Consequently, exceeding the threshold was associated with widened disparities, including greater reductions in outpatient service use (disparity: -6.2 services per person-year; 95% CI, -11.7 to -0.6; P = .03) and medication fills (disparity: -7.2 fills per person-year; 95% CI, -13.4 to -1.0; P = .02) among Black and Hispanic vs White beneficiaries. Conclusions and Relevance: This cross-sectional study found that loss of eligibility for Medicaid supplemental insurance above the federal poverty level, which increases cost sharing in Medicare, was associated with increased racial and ethnic health care disparities among low-income Medicare beneficiaries. Expanding eligibility for Medicaid supplemental insurance may narrow these disparities.

Care Experiences and Visit Use of Physician and Nonphysician Medicare Patients.

This cross-sectional study compares care experiences and outpatient visit use between physician-patients and nonphysician-patients.

Performance on Patient Experience Measures of Former Chief Medical Residents as Physician Exemplars Chosen by the Profession.

Importance: Physicians' knowledge about each other's quality is central to clinical decision-making, but such information is not well understood and is rarely harnessed to identify exemplars for disseminating best practices or quality improvement. One exception is chief medical resident selection, which is typically based on interpersonal, teaching, and clinical skills. Objective: To compare care for patients of primary care physicians (PCPs) who were former chiefs with care for patients of nonchief PCPs. Design, Setting, and Participants: Using 2010 to 2018 Medicare Fee-For-Service Consumer Assessment of Healthcare Providers and Systems (CAHPS) survey data (response rate, 47.6%), Medicare claims for random 20% samples of fee-for-service beneficiaries, and medical board data from 4 large US states, we compared care for patients of former chief PCPs with care for patients of nonchief PCPs in the same practice using linear regression. Data were analyzed from August 2020 to January 2023. Exposures: Receiving the plurality of primary care office visits from a former chief PCP. Main Outcomes and Measures: Composite of 12 patient experience items as primary outcome and 4 spending and utilization measures as secondary outcomes. Results: The CAHPS samples included 4493 patients with former chief PCPs and 41 278 patients with nonchief PCPs. The 2 groups were similar in age (mean [SD], 73.1 [10.3] years vs 73.2 [10.3] years), sex (56.8% vs 56.8% female), race and ethnicity (1.2% vs 1.0% American Indian or Alaska Native, 1.3% vs 1.9% Asian or Pacific Islander, 4.8% vs. 5.6% Hispanic, 7.3% vs 6.6% non-Hispanic Black, and 81.5% vs. 80.0% non-Hispanic White), and other characteristics. The Medicare claims for random 20% samples included 289 728 patients with former chief PCPs and 2 954 120 patients with nonchief PCPs. Patients of former chief PCPs rated their care experiences significantly better than patients of nonchief PCPs (adjusted difference in composite, 1.6 percentage points; 95% CI, 0.4-2.8; effect size of 0.30 standard deviations (SD) of the physician-level distribution of performance; P = .01), including markedly higher ratings of physician-specific communication and interpersonal skills typically emphasized in chief selection. Differences were large for patients of racial and ethnic minority groups (1.16 SD), dual-eligible patients (0.81 SD), and those with less education (0.44 SD) but did not vary significantly across groups. Differences in spending and utilization were minimal overall. Conclusions and Relevance: In this study, patients of PCPs who were former chief medical residents reported better care experiences than patients of other PCPs in the same practice, especially for physician-specific items. The study results suggest that the profession possesses information about physician quality, motivating the development and study of strategies for harnessing such information to select and repurpose exemplars for quality improvement.

Organization and Performance of US Health Systems.

Importance: Health systems play a central role in the delivery of health care, but relatively little is known about these organizations and their performance. Objective: To (1) identify and describe health systems in the United States; (2) assess differences between physicians and hospitals in and outside of health systems; and (3) compare quality and cost of care delivered by physicians and hospitals in and outside of health systems. Evidence Review: Health systems were defined as groups of commonly owned or managed entities that included at least 1 general acute care hospital, 10 primary care physicians, and 50 total physicians located within a single hospital referral region. They were identified using Centers for Medicare & Medicaid Services administrative data, Internal Revenue Service filings, Medicare and commercial claims, and other data. Health systems were categorized as academic, public, large for-profit, large nonprofit, or other private systems. Quality of preventive care, chronic disease management, patient experience, low-value care, mortality, hospital readmissions, and spending were assessed for Medicare beneficiaries attributed to system and nonsystem physicians. Prices for physician and hospital services and total spending were assessed in 2018 commercial claims data. Outcomes were adjusted for patient characteristics and geographic area. Findings: A total of 580 health systems were identified and varied greatly in size. Systems accounted for 40% of physicians and 84% of general acute care hospital beds and delivered primary care to 41% of traditional Medicare beneficiaries. Academic and large nonprofit systems accounted for a majority of system physicians (80%) and system hospital beds (64%). System hospitals were larger than nonsystem hospitals (67% vs 23% with >100 beds), as were system physician practices (74% vs 12% with >100 physicians). Performance on measures of preventive care, clinical quality, and patient experience was modestly higher for health system physicians and hospitals than for nonsystem physicians and hospitals. Prices paid to health system physicians and hospitals were significantly higher than prices paid to nonsystem physicians and hospitals (12%-26% higher for physician services, 31% for hospital services). Adjusting for practice size attenuated health systems differences on quality measures, but price differences for small and medium practices remained large. Conclusions and Relevance: In 2018, health system physicians and hospitals delivered a large portion of medical services. Performance on clinical quality and patient experience measures was marginally better in systems but spending and prices were substantially higher. This was especially true for small practices. Small quality differentials combined with large price differentials suggests that health systems have not, on average, realized their potential for better care at equal or lower cost.

Physician-Peer Relationships and Patient Experiences With Specialist Care.

Importance: Peer relationships may motivate physicians to aspire to high professional standards but have not been a major focus of quality improvement efforts. Objective: To determine whether peer relationships between primary care physicians (PCPs) and specialists formed during training motivate improved specialist care for patients. Design, Setting, and Participants: In this quasi-experimental study, difference-in-differences analysis was used to estimate differences in experiences with specialist care reported by patients of the same PCP for specialists who did vs did not co-train with the PCP, controlling for any differences in patient ratings of the same specialists in the absence of co-training ties. Specialist visits resulting from PCP referrals from 2016 to 2019 in a large health system were analyzed, including a subset of undirected referrals in which PCPs did not specify a specialist. Data were collected from January 2016 to December 2019 and analyzed from March 2020 to October 2022. Exposure: The exposure was PCP-specialist overlap in training (medical school or postgraduate medical) at the same institution for at least 1 year (co-training). Main Outcomes and Measures: Composite patient experience rating of specialist care constructed from Press Ganey's Medical Practice Survey. Results: Of 9920 specialist visits for 8655 patients (62.9% female; mean age, 57.4 years) with 502 specialists in 13 specialties, 3.1% (306) involved PCP-specialist dyads with a co-training tie. Co-training ties between PCPs and specialists were associated with a 9.0 percentage point higher adjusted composite patient rating of specialist care (95% CI, 5.6-12.4 percentage points; P < .001), analogous to improvement from the median to the 91st percentile of specialist performance. This association was stronger for PCP-specialist dyads with full temporal overlap in training (same class or cohort) and consistently strong for 9 of 10 patient experience items, including clarity of communication and engagement in shared decision-making. In secondary analyses of objective markers of altered specialist practice in an expanded sample of visits not limited by the availability of patient experience data, co-training was associated with changes in medication prescribing, suggesting behavioral changes beyond interpersonal communication. Patient characteristics varied minimally by co-training status of PCP-specialist dyads. Results were similar in analyses restricted to undirected referrals (in which PCPs did not specify a specialist). Concordance between PCPs and specialists in physician age, sex, medical school graduation year, and training institution (without requiring temporal overlap) was not associated with better care experiences. Conclusions and Relevance: In this quasi-experimental study, PCP-specialist co-training elicited changes in specialist care that substantially improved patient experiences, suggesting potential gains from strategies encouraging the formation of stronger physician-peer relationships.

Risk Adjustment And Promoting Health Equity In Population-Based Payment: Concepts And Evidence.

The objective of risk adjustment is not to predict spending accurately but to support the social goals of a payment system, which include equity. Setting population-based payments at accurate predictions risks entrenching spending levels that are insufficient to mitigate the impact of social determinants on health care use and effectiveness. Instead, to advance equity, payments must be set above current levels of spending for historically disadvantaged groups. In analyses intended to guide such reallocations, we found that current risk adjustment for the community-dwelling Medicare population overpredicts annual spending for Black and Hispanic beneficiaries by $376-$1,264. The risk-adjusted spending for these populations is lower than spending for White beneficiaries despite the former populations' worse risk-adjusted health and functional status. Thus, continued movement from fee-for-service to population-based payment models that omit race and ethnicity from risk adjustment (as current models do) should result in sizable resource reallocations and incentives that support efforts to address racial and ethnic disparities in care. We found smaller overpredictions for less-educated beneficiaries and communities with higher proportions of residents who are Black, Hispanic, or less educated, suggesting that additional payment adjustments that depart from predictive accuracy are needed to support health equity. These findings also suggest that adding social risk factors as predictors to spending models used for risk adjustment may be counterproductive or accomplish little.

The merits of administrative benchmarks for population-based payment programs.

The different approaches to setting benchmarks for population-based payment models (empirical, bidding based, and administratively set) have unique advantages and challenges.

Hospital-Administered Cancer Therapy Prices for Patients With Private Health Insurance.

Importance: The federal Hospital Price Transparency final rule, which became effective in 2021, requires hospitals to publicly disclose payer-specific prices for drugs. However, little is known about hospital markup prices for parenterally administered therapies. Objective: To assess the extent of price markup by hospitals on parenterally administered cancer therapies and price variation among hospitals and between payers at each hospital. Design, Setting, and Participants: A cross-sectional analysis was conducted of private payer-specific negotiated prices for the top 25 parenteral (eg, injectable or infusible) cancer therapies by Medicare Part B spending in 2019 using publicly available hospital price transparency files. Sixty-one National Cancer Institute (NCI)-designated cancer centers providing clinical care to adults with cancer were included. The study was conducted from April 1 to October 15, 2021. Exposures: Estimated hospital acquisition costs for each cancer therapy using participation data from the federal 340B Drug Pricing Program. Main Outcomes and Measures: The primary outcome was hospital price markup for each cancer therapy in excess of estimated acquisition costs. Secondary outcomes were the extent of across-center price ratios, defined as the ratio between the 90th percentile and 10th percentile median prices across centers, and within-center price ratios, defined as the ratio between the 90th percentile and 10th percentile prices between payers at each center. Results: Of 61 NCI-designated cancer centers, 27 (44.3%) disclosed private payer-specific prices for at least 1 top-selling cancer therapy as required by federal regulations. Median drug price markups across all centers and payers ranged between 118.4% (sipuleucel-T) and 633.6% (leuprolide). Across-center price ratios ranged between 2.2 (pertuzumab) and 15.8 (leuprolide). Negotiated prices also varied considerably between payers at the same center; median within-center price ratios for cancer therapies ranged from 1.8 (brentuximab) to 2.5 (bevacizumab). Conclusions and Relevance: Most NCI-designated cancer centers did not publicly disclose payer-specific prices for cancer therapies as required by federal regulation. The findings of this cross-sectional study suggest that, to reduce the financial burden of cancer treatment for patients, institution of public policies to discourage or prevent excessive hospital price markups on parenteral chemotherapeutics might be beneficial.

Difference-in-differences for categorical outcomes.

OBJECTIVE: To discuss and develop difference-in-difference estimators for categorical outcomes and apply them to estimate the effect of the Affordable Care Act's Medicaid expansion on insurance coverage. DATA SOURCES: Secondary analysis of Survey on Income and Program Participation (SIPP) data on health insurance coverage types before (January 2013) and after (December 2015) Medicaid expansion in 39 US states (19 expansion and 20 non-expansion). STUDY DESIGN: We develop difference-in-difference methods for repeated measures (panel data) of categorical outcomes. We discuss scale-dependence of DID assumptions for marginal and transition effect estimates and specify a new target estimand: the difference between outcome category transitions under treatment versus no treatment. We establish causal assumptions about transitions that are sufficient to identify this and a marginal target estimand. We contrast the marginal estimands identified by the transition approach versus an additive assumption only about marginal evolution. We apply both the marginal and transition approaches to estimate the effects of Medicaid expansion on health insurance coverage types (employer-sponsored; other private, non-group; public; and uninsured). DATA EXTRACTION: We analyzed 16,027 individual survey responses from people aged 18-62 years in the 2014 SIPP panel. PRINCIPAL FINDINGS: We show that the two identifying assumptions are equivalent (on the scale of the marginals) if either the baseline marginal distributions are identical or the marginals are constant in both groups. Applying our transitions approach to the SIPP data, we estimate a differential increase in transitions from uninsured to public coverage and differential decreases in transitions from uninsured to private, non-group coverage and in remaining uninsured. CONCLUSIONS: By comparing the assumption that marginals are evolving in parallel to an assumption about transitions across outcome values, we illustrate the scale-dependence of difference-in-differences. Our application shows that studying transitions can illuminate nuances obscured by changes in the marginals.

ACO Investment Model Produced Savings, But The Majority Of Participants Exited When Faced With Downside Risk.

Medicare's Accountable Care Organization (ACO) Investment Model (AIM) provided up-front funding to forty-one small, rurally located ACOs to encourage their participation in the Medicare Shared Savings Program. We estimate net savings to Medicare of $381.5 million over three years, driven by utilization reductions in inpatient and other institutional care and by the absence of shared risk for potential increases in Medicare spending incurred by participants. These savings suggest that population-based payment models can enable providers to better meet the needs of rural populations through greater flexibility in care delivery. However, nearly two-thirds of AIM ACOs exited the Medicare Shared Savings Program when faced with the requirement to assume downside financial risk, starting in year four of participation. As the Centers for Medicare and Medicaid Services builds on AIM and rural hospital global payment models, our findings suggest that new payment models can support more efficient use of resources to meet the health care needs of rural populations. However, the findings also caution against the vigorous pursuit of savings as a primary goal of payment models in traditionally underserved communities.

Residual Confounding in Health Plan Performance Assessments: Evidence From Randomization in Medicaid.

BACKGROUND: Risk adjustment is used widely in payment systems and performance assessments, but the extent to which it distinguishes plan or provider effects from confounding due to patient differences is typically unknown. OBJECTIVE: To assess the degree to which risk-adjusted measures of health plan performance adequately adjust for the variation across plans that arises because of differences in patient characteristics (residual confounding). DESIGN: Comparison between plan performance estimates based on enrollees who made plan choices (observational population) and estimates based on enrollees assigned to plans (randomized population). SETTING: Natural experiment in which more than two thirds of a state's Medicaid population in 1 region was randomly assigned to 1 of 5 plans. PARTICIPANTS: 137 933 enrollees in 2013 to 2014, of whom 31.1% selected a plan and 68.9% were randomly assigned to 1 of the same 5 plans. MEASUREMENTS: Annual total spending (that is, payments to providers), primary care use, dental care use, and avoidable emergency department visits, all scored as plan-specific deviations from the "average" plan performance within each population. RESULTS: Enrollee characteristics were appreciably imbalanced across plans in the observational population, as expected, but were not in the randomized population. Annual total spending varied across plans more in the observational population (SD, $147 per enrollee) than in the randomized population (SD, $70 per enrollee) after accounting for baseline differences in the observational and randomized populations and for differences across plans. On average, a plan's spending score (its deviation from the "average" performance) in the observational population differed from its score in the randomized population by $67 per enrollee in absolute value (95% CI, $38 to $123), or 4.2% of mean spending per enrollee (P = 0.009, rejecting the null hypothesis that this difference would be expected from sampling error). The difference was reduced modestly by risk adjustment to $62 per enrollee (P = 0.012). Residual confounding was similarly substantial for most other performance measures. Further adjustment for social factors did not materially change estimates. LIMITATION: Potential heterogeneity in plan effects between the 2 populations. CONCLUSION: Residual confounding in risk-adjusted performance assessments can be substantial and should caution policymakers against assuming that risk adjustment isolates real differences in plan performance. PRIMARY FUNDING SOURCE: Arnold Ventures.

Coding-Driven Changes In Measured Risk In Accountable Care Organizations.

Claims data, which form the foundation of risk adjustment in payment for health care services, may reflect efforts to capture more-or more severe-clinical conditions rather than true changes in health status. This can distort payments. We quantify this in the context of Medicare's accountable care organization (ACO) program by comparing risk scores derived from two different measurement approaches. One approach uses diagnoses coded on claims based on Centers for Medicare and Medicaid Services Hierarchical Condition Categories (HCC), and the other uses self-reported, survey-based health data from the Consumer Assessment of Healthcare Providers and Systems (CAHPS). During 2013-16 HCC-based risk scores grew faster than CAHPS-based risk scores (2.1 percent versus 0.3 percent annually), and the gap in HCC- and CAHPS-based risk score growth varied widely across ACOs. The average gap in risk score growth appears to be the result primarily of HCC coding practices rather than poor performance of the CAHPS model, suggesting that coding practices (not necessarily driven by ACO contracts) may account for most of the observed risk score growth for ACO beneficiaries.