Correspondence to: Joseph Lipscomb, PhD, Department of Health Policy and Management, Rollins School of Public Health, Emory University, Atlanta, GA 30322 (e-mail: jlipsco{at}sph.emory.edu).
Proponents of managed care extol its potential to control costs and improve quality through an emphasis on prevention, screening, and treatment that is evidence based, coordinated, and prudent in the use of public and private dollars. The focus is on promoting wellness, a winwin situation from the standpoint of both health outcomes and costs.
Critics counter that managed care organizationsbudget constrained and unable to fully capture the potential cost savings from aggressive prevention and screening because of inevitable fluctuations in plan enrollmentactually have substantial incentives to limit access to care. Specifically, managed care organizations seek to control costs by modulating the volume and mix of services through a combination of provider incentives and restraints, limits on investments in technology and infrastructure, and a maze of price and nonprice barriers imposed on enrollees.
The complex truth of the matter surely lies somewhere between these two stylized characterizations. This becomes quickly evident from any survey of the large, empirically rich health services research literature in this general area over the past three decades.
At the moment, innovative research to better understand the structure, performance, and overall impact of managed health care is more pressing and more challenging than ever before. It is more pressing because, at least in the United States, private employers and governments at all levels will continue to rely on, and may accelerate the adoption of, managed care as a vehicle for controlling costs. It is more challenging because managed care has evolved over time from the comparatively monolithic, prepaid group practicebased health maintenance organization (HMO) model to a multiplicity of organizational forms, including several variants of the HMO, preferred provider organizations (PPOs), point-of-service (POS) plans, and various hybrid models (1).
In 2001, about 28% of the U.S. population was enrolled in HMOs (including POS plans) and a possibly larger fraction was enrolled in PPOs. [Reliable estimates of PPO enrollment in the United States are hard to come by, but America's Health Insurance Plans (formerly known as the American Association of Health Plans) reports (2) that total U.S. HMO enrollment in 1998 was about 79 million, whereas total PPO enrollment in 1997 was 89 million.] Also in 2001, about 16% of all Medicare enrollees and 57% of Medicaid enrollees were in some form of managed care (3). Such numbers suggest, first, that this hydra-headed phenomenon called managed care is sufficiently pervasive that it may have profound effects on the structure and functioning of health care markets in many parts of the nationinfluencing cost, access, and quality not only for managed care enrollees but also for those still covered by fee-for-service insurance (as well as the uninsured). Second, because millions of Americans are still not in managed care, including the great majority of Medicare beneficiaries, it is vitally important to understand the nature and extent of these managed caregenerated spillover effects.
In fact, over the past decade, a growing body of literature has investigated such spillover effects, much of it focused on the relationship between managed care penetration (market share) in geographically defined health care markets and expenditures per capita for fee-for-service enrollees in the same area (4). As Baker summarizes, "...this literature as a whole suggests that managed care is capable of having broad influences on the health care delivery system, and that these effects have been in the direction of driving down health care costs" (4). Similarly, Baker reports that higher managed care market concentration is associated with slower adoption of new technologies (particularly expensive ones) and other infrastructure investment. But the literature on the question of whether managed care spillover effects extend to patterns of service use, patient outcomes, and quality of care is much thinner and the evidence more indirect and equivocal. [One intriguing exception is an analysis (5) that found that greater managed care market concentration was associated with a consolidation of mammography service availability, although there were no differences between breast cancer stage-of-diagnosis patterns or mortality rates between high and lowmanaged care areas.]
Hence the importance of the conclusions reached by Keating et al. (6) in their well-executed analysis in this issue of the Journal. For six of their eight well-documented quality-of-care indicators covering aspects of breast and colorectal cancer treatment, there was no association between Medicare managed care market share and the likelihood that a Medicare fee-for-service patient would receive guideline-indicated therapy.
To derive their conclusions, the investigators used data from the Surveillance, Epidemiology and End Results (SEER1) registries linked to Medicare claims data to examine the care received by over 41 000 breast cancer patients and over 48 000 colorectal cancer patients newly diagnosed during 19931999. For each of the 202 U.S. counties covered by SEER, managed care penetration was indexed by the ratio of beneficiaries enrolled in managed care to all Medicare beneficiaries in the county. Each Medicare fee-for-service patient was assigned to one of four Medicare managed care market share categories corresponding to county of residence: <1%, 1%10%, >10%30%, or >30%. For each of the eight quality-of-care indicators, patient level logistic regression modeling was used to derive the impact of a county's managed care market share category on the likelihood that a Medicare fee-for-service patient residing in the county would receive the indicated patient care. To adjust for patient-level factors that could influence the receipt of cancer care, control variables were included for patient age, race, ethnicity, and marital status; clinical features of the diagnosed tumor; the extent of concurrent comorbid illnesses; and the patient's income and education (assigned on the basis of census track of residence). To adjust for the possibility that unobserved factors within the patient's market area might independently influence both the time trend in managed care market share there and the propensity to use certain cancer services, the investigators included the patient's county of residence as a fixed-effect variable in these pooled cross-sectional regressions.
Should we infer from this soundly done investigation that the managed care spillover is over, or perhaps never quite began, as far as cancer interventions and quality of care are concerned? Perhaps. Yet we need to take account now of at least two other studies [not discussed in Keating et al. (6)] indicating that managed care market penetration may in fact influence the cancer interventions received by those with fee-for-service coverage (7,8).
One study, by Baker and McClellan (7), analyzed treatment patterns for breast, colorectal, lung, and prostate cancers in a 19921994 national cohort of Medicare enrollees. The authors concluded that, on balance, managed care penetration is associated with differences in practice patterns for fee-for-service patients. Specifically, although breast cancer measures (related to mastectomy, lumpectomy, and radiation use) were not influenced by the prevalence of managed care in the patient's market area, substantial spillover effects were found for measures of colorectal cancer treatment (local excision, partial colectomy, and major resection), lung cancer treatment (excision, lobectomy, and pneumonectomy), and prostate cancer treatment (radical prostatectomy and radiation therapy).
The analysis strategies adopted by Baker and McClellan and by Keating et al. were broadly compatible in a number of respects, though differing in how several important variables were operationally defined and in some technical aspects of the logistic regression modeling. For example, Baker and McClellan defined managed care penetration in terms of the fraction of all individuals (not just Medicare beneficiaries) in the market enrolled in HMOs (their proxy for all forms of managed care), and cancer care markets consisted not of counties but of the 322 U.S. standard Metropolitan Statistical Areas (MSAs). Incident cancer cases were identified not by registries but by subjecting Medicare claims data to an algorithm reported to have 80% sensitivity and specificity. To control for possible unobserved MSAspecific differences that would independently influence managed care market share and the propensity to receive the targeted therapies, Baker and McClellan included control variables for MSA cancer diagnosis and treatment rates in Medicare over the 19851987 period. However, whereas Keating et al. selected guideline-endorsed treatments for their quality-of-care analysis, Baker and McClellan focused on "some of the most important treatment options, in terms of...resource use and possibly cancer outcomes." Whether that nuanced difference in characterization matters in the comparative interpretation of findings is not clear. What is clear is that these two well-executed analyses have yielded (except notably for breast cancer) generally divergent findings. It may be that managed care spillover effects are sensitive to the time frame of analysis, the cancer disease site, the precise mix of managed care mechanisms (HMO, PPO, PSO) operating in the relevant market areas, and/or a host of other factors that require further probing.
Indeed, the study of Baker et al. (8) provides evidence that spillover effects can arise elsewhere along the cancer care continuum. Their analysis of data drawn from the 1996 Medical Expenditure Panel Survey showed that increases in HMO market penetration were associated with increases in appropriate use of screening mammography, clinical breast exams, and Pap smears. [These findings are consistent with those of an earlier study on spillover effects in screening mammography by Phillips et al. (9).] In a subgroup analysis, Baker et al. (8) observed that the positive association between HMO market penetration and screening rates was statistically significant for only those individuals not enrolled in managed carelending added support to the spillover hypothesis, at least for cancer screening. In contrast to the findings about HMO market share, there was no relationship between an index of PPO market share and cancer screening rates.
Interestingly, there was no association between HMO penetration and prostate cancer screening (8). Baker et al. note that both breast and cervical screening have long been endorsed by the U.S. Preventive Services Task Force. Both interventions are also included in the National Committee for Quality Assurance's Health Plan Employer Data and Information Set (HEDIS), the yardstick of managed care performance most widely used by private purchasers of health care. Prostate cancer screening, by contrast, is neither recommended by the Task Force nor included in HEDIS. Consequently, it is not unreasonable to conclude that the longer and stronger an intervention's endorsement by respected bodies, the greater the chance it will spill over into general practice within the local market (all else equal).
In light of this array of findings, what should be done next? Building on Keating et al., Baker and McClellan, other contributions from the spillover literature, and more than a decade of SEERMedicare investigations, we should launch a new wave of studies to strengthen our knowledge of the ways and means by which the quality of cancer care varies across populations and over time. Specifically, the National Cancer Institute (NCI), the Centers for Medicare and Medicaid Services (CMS), the Centers for Disease Control and Prevention (CDC), and the Agency for Healthcare Research and Quality (AHRQ) should consider partnering to support an expanded, coordinated, ongoing program of extramural and in-house research to track targeted aspects of cancer care quality nationally. Important ongoing efforts, led by NCI and CDC and involving AHRQ, to monitor and interpret trends in appropriate cancer screening are already underway (10). The greatest new opportunities to enhance cancer quality assessment at the population level lie in the domains of diagnosis, treatment, survivorship, and end-of-life care.
The best way to proceed would be to select a suite of evidence-based quality-of-care indicators that are also amenable to analysis through SEER-Medicare, in the spirit of this NCI-supported work by Keating et al. Multiple cancer disease sites would be examined concurrently. Quality indicators would be based on prominent guideline recommendations and also on the "voluntary consensus standard" measures emerging from the ongoing National Quality Forum's Cancer Care Quality Measures Project (http://www.qualityforum.org/txcancer1pagerFinalAllLists.pdf). (In fact, NCI, CDC, CMS, and AHRQ have already teamed up to financially underwrite and provide substantive support to help launch this project. In addition, CMS and NCI announced in 2004 a multipart collaboration to improve the process for bringing cancer drugs to patients, including the addition of CMS claims data to NCI's bioinformatics grid [CaBIG; see http://www.cms.hhs.gov/media/press/release.asp?Counter=1084]. Note also the long-time partnerships involving NCI, CMS, the SEER registries, and AHRQ to make available and encourage extramural investigators to use SEER-Medicare data for surveillance and economic analyses [see http://healthservices.cancer.gov].) Over time, as data capabilities continue to strengthen, the analyses would also employ registry data (from SEER or the CDC's National Program of Cancer Registries) linked to Medicaid and private-payer administrative data to expand population level cancer quality tracking to those under 65 years of age.
At the same time (again in the spirit of Keating et al.), these analyses would attempt to identify and understand managed care spillover effects and possibly other mechanisms that shape the organization and performance of health care markets. For example, there may be a subtle interplay between spillover effects for cancer screening and treatment. If higher managed care penetration leads to higher screening rates, we may expect to see a higher fraction of cases diagnosed at earlier stages. Over time, such a stage shift could induce a shift in treatment patterns over and above whatever direct effects managed care penetration has on patterns of care via the mechanisms discussed by Keating et al. To better analyze these and other complexities, researchers need market share data at the county or MSA level, differentiated by type of managed care organization (HMO, PPO, POS, and so on).
Such an ongoing set of investigations would set the stage for tracking and probing the impacts of important new policies, such as pay-for-performance, on cancer care quality across the population and over time. Concurrently, we would learn ever more about whether and how the market penetration of various species of managed care influences, for good or ill, the performance of the health care marketplace.
NOTES
1 Editor's note: SEER is a set of geographically defined, population-based, central cancer registries in the United States, operated by local nonprofit organizations under contract to the NCI. Registry data are submitted electronically without personal identifiers to the NCI on a biannual basis, and the NCI makes the data available to the public for scientific research.
REFERENCES
(1) Academy Health. Glossary of terms commonly used in health care. Available at: http://www.academyhealth.org/publications/glossary.pdf. [Last accessed: January 8, 2005.]
(2) America's Health Insurance Plans. Enrollment, growth, accreditation. Available at: http://www.ahip.org/content/default.aspx?bc=41|331|358. [Last accessed: January 8, 2005.]
(3) National Center for Health Statistics. Health, United States, 2004, with Chartbook on Trends in Health of Americans. Hyattsville, MD: 2004, Table 152 (p.384), Table 150 (p. 380), and Table 151 (p. 382).
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(8) Baker LC, Phillips KA, Haas JS, Liang S-Y, Sooneborn, D. The effect of area HMO market share on cancer screening. Health Serv Res 2004;39:175172.[CrossRef][Medline]
(9) Phillips KA, Kerlikowske K, Baker LC, Chang SW, Brown ML. Factors associated with women's adherence to mammography screening guidelines. Health Serv Res 1998;33:2953.[ISI][Medline]
(10) Hiatt RA, Klabunde C, Breen N, Swan J, Ballard-Barbash, R. Cancer screening practices from the National Health Interview Surveys: past, present, and future. J Natl Cancer Inst 2002;94:183746.
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