What Do We Know About Health Care Access and Quality in Medicare Advantage Versus the Traditional Medicare Program?

Summary of Findings and Conclusions

This literature review included 45 studies published between 2001 and 2014 that examined how Medicare Advantage might affect health care quality and access to care, including 40 studies that made direct comparisons between Medicare health plans and traditional Medicare. As a body of work, these studies offer some insights, although the work is limited by shortfalls in the timeliness of data, the range of health plans studied and the comprehensiveness of the metrics available, particularly on a national basis. Recent studies still mainly capture the Medicare HMO experience rather than experience across the diversity of health plans now participating in Medicare Advantage, and none of them are current enough to provide insight on how Medicare Advantage compares to traditional Medicare after 2010. While many of the reviewed studies adjust for differences in location, patient mix, and health status between Medicare Advantage and traditional Medicare in some fashion, some studies do this better than others, and many studies are constrained by limitations in the available data. In addition, few studies (only four) examine in depth the particular experience of those who are less healthy, functionally impaired, or have other characteristics that make them relatively high users of medical care and potentially disproportionately vulnerable to poorer quality of care or access problems.

The review of the literature, 45 studies published between 2000 and 2014, comparing quality of care and access provided under traditional Medicare and Medicare Advantage plans, suggests the following:

• HEDIS Effectiveness Metrics on Preventive Care. Medicare Advantage, on average, scores more highly than traditional Medicare on subsets of Medicare HEDIS indicators – primarily those pertaining to use of preventive care services. Two studies found Medicare preferred provider organizations (PPOs) outperformed traditional Medicare on some metrics (particularly mammography rates), though HMOs nevertheless performed better than PPOs. All of these studies were conducted prior to changes made by the ACA to improve coverage of preventive services under traditional Medicare.
• Beneficiary Reports on Quality and Access (CAHPS). Medicare beneficiaries generally rated Medicare Advantage lower than traditional Medicare on questions about health care access and quality, especially if beneficiaries had a chronic illness or were sick; however, the difference in ratings between traditional Medicare and Medicare Advantage narrowed on some metrics by 2009 (e.g., overall care ratings). Keenan et al. 2009 found that sick beneficiaries in Medicare Advantage rated their plans substantially lower than beneficiaries of similar health status in traditional Medicare, and Elliott et al. 2011 found significantly lower CAHPS ratings (and greater disparities between Medicare Advantage and traditional Medicare) among vulnerable subgroups of beneficiaries in Medicare Advantage. Little is known about how CAHPS scores vary by type of Medicare Advantage plan since most studies are based on HMOs or periods in which HMOs were the main plan type.
• Potentially Avoidable Hospital Admissions. Based on six studies involving beneficiaries in a limited number of states and/or plans represented by the Alliance of Community Health Plans (ACHP), Medicare beneficiaries in HMOs are less likely to be hospitalized for a potentially avoidable admission than beneficiaries in traditional Medicare. Four of these studies rely on data prior to 2006, and reflect HMO experiences in mature markets.
• Readmission Rates. While a number of studies examine whether readmission rates differ among beneficiaries in Medicare Advantage and traditional Medicare, the evidence from these studies is inconclusive because findings differ across the studies and many studies lack adjustments for important potentially confounding factors.
• Health Outcomes. There is some evidence that good coverage, as defined by relatively low cost-sharing (whether through Medicare HMOs or through Medicare with supplemental coverage), may result in earlier diagnoses of some cancers compared to traditional Medicare alone. Treatment patterns for some cancers also may differ between Medicare HMOs and traditional Medicare, but studies do not show that this affects patient outcomes. However, the age of the studies, the gaps in controls for selection, and the evolving nature of guidelines for appropriate care limit the conclusions that can be drawn.
• Resource Utilization. Medicare HMOs appear to provide a less resource-intensive style of practice than traditional Medicare, as measured in studies examining end-of-life care, use of certain procedures, and overall utilization rate in HMOs, especially for hospital services. However, most of these studies provide little direct evidence of whether less intensive care is better or worse or how the appropriateness of care differs between Medicare Advantage and traditional Medicare.
• Variation by Geography, by Plan Type, and by Plan Experience. On a variety of metrics, performance among Medicare Advantage plans varies substantially across plans, even among plans of the same plan type. The variations by market in more established HMOs with integrated delivery systems tend to be more represented in existing research, and to perform better. Performance on quality and access metrics varies across geographic areas, and the variations in Medicare Advantage and traditional Medicare ratings are not necessarily the same.

In summary, despite great interest in comparisons between traditional Medicare and Medicare Advantage, studies comparing overall quality and access to care between Medicare Advantage plans and traditional Medicare tend to be limited.

On the one hand, the evidence indicates that Medicare HMOs tend to perform better than traditional Medicare in providing preventive services and using resources more conservatively, at least through 2009. These are metrics where HMOs have historically been strong. On the other hand, beneficiaries continue to rate traditional Medicare more favorably than Medicare Advantage plans in terms of quality and access, such as overall care and plan rating, though one study suggests that the difference may be narrowing between traditional Medicare and Medicare Advantage for the average beneficiary. Among beneficiaries who are sick, the differential between traditional Medicare and Medicare Advantage is particularly large (relative to those who are healthy). Very few studies include evidence based on all types of Medicare Advantage plans, including analysis of performance for newer models, such as local and regional PPOs whose enrollment is growing.

As the beneficiary population ages, better evidence is needed on how Medicare Advantage plans perform relative to traditional Medicare for patients with significant medical needs that make them particularly vulnerable to poorer outcomes. The ability to assess quality and access for such subgroups is limited because many data sources do not allow subgroups to be identified or have too small a sample size to support estimates. Also, in many cases, metrics employed may not be specific to the particular needs or the way a patient’s overall health and functional status or other comorbid conditions influence the care they receive for particular services.

At a time when enrollment in Medicare Advantage is growing, it is disappointing that better information is not available to support policymaking on this program. Our findings highlight the gaps in available evidence and reinforce the potential value of strengthening available data and other support for tracking and monitoring performance across Medicare Advantage plans and traditional Medicare as each sector evolves.