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US Preventive Services Task Force. Guide to Clinical Preventive Services: Report of the U.S. Preventive Services Task Force. 2nd edition. Baltimore (MD): Williams & Wilkins; 1996.

  • This publication is provided for historical reference only and the information may be out of date.

This publication is provided for historical reference only and the information may be out of date.

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Guide to Clinical Preventive Services: Report of the U.S. Preventive Services Task Force. 2nd edition.

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vCost-Effectiveness and Clinical Preventive Services

Documented effectiveness is -- or generally should be -- the most basic requirement for providing a health care service. It is a particularly important prerequisite for preventive services, where the clinician has a compelling responsibility to "do no harm" to healthy patients. The fundamental role of effectiveness for clinical decisions motivated the U.S. Preventive Services Task Force effort to evaluate the evidence of effectiveness for clinical preventive services, and the Task Force recommendations in the following chapters are reflections of this evidence.

Effectiveness alone, however, is not a sufficient basis to initiate services in most practical health care contexts. Factors other than effectiveness, reflecting the immediate trade-offs and broad implications of providing a service, are relevant to the goals and the practical constraints confronted by every decision maker. Chapter i describes several of these factors, and they are cited in the subsequent chapters when they are likely to be relevant to a clinician's decision. The present chapter focuses on a single approach, cost-effectiveness analysis, that can combine information on the health benefits, health risks, and costs of health care services. Although cost-effectiveness analysis was not the basis of recommendations in this edition of the Guide, this chapter should alert readers that the Task Force believes such analyses should have an increasing role in individual and public policy decisions about providing preventive services as the analytic methodology matures.

Properly used, cost-effectiveness analysis incorporates and complements evidence of effectiveness to inform recommendations on clinical preventive and other health care services. It is intended not to substitute mechanically for complex decision-making processes but rather to be used in combination with other evidence. Efforts to enable cost-effectiveness analysis to be more easily, systematically, and usefully considered in policy decisions are under way. The work of the Panel on Cost-Effectiveness in Health and Medicine (PCEHM), convened in 1993, complements the work of the Task Force in the area of cost-effectiveness analysis. The PCEHM is working to standardize methodology, provide guidelines for cost-effectiveness analysis, and resolve technical differences among studies to improve their quality and comparability. The work of this group will be an important resource for those organizations formulating policy related to clinical preventive services.

Assessing the Cost-Effectiveness of Interventions

Cost-effectiveness analysis is a method for assessing and summarizing the value of a medical technology, practice, or policy.1,2 Underlying the methodology is the assumption that the resources available to spend on health care are constrained, whether from the societal, organizational, practitioner, or patient point of view. Cost-effectiveness information is intended to inform decisions about health care investments within this finite budget. The cost-effectiveness ratio summarizes information on cost and effect, allowing interventions to be compared on the basis of their worth and priority to the patient, society in general, or some other constituency. Although the cost-effectiveness ratio takes the form of a price -- that is, a dollar cost per unit of effect -- it is generally interpreted in the inverse manner, as a measure of the benefit achievable for a given level of resources.

The cost-effectiveness ratio encapsulates a defined set of information. 3 The numerator of the ratio summarizes the costs and financial savings associated with the intervention, including the costs of the intervention itself, side effects, and savings from avoided illness and disability. These costs consist of both medical costs (e.g., physician visits, hospitalization, treatment) and nonmedical costs (e.g., transportation, caretaker) associated with the intervention or the illness.

The denominator of the cost-effectiveness ratio reflects the health effect of the intervention. This feature of cost-effectiveness analysis distinguishes it from cost-benefit analysis, in which health benefits are translated into dollars. The year of life saved is probably the most commonly used measure of the health effect. Years of life saved may be adjusted for the quality of life of those years, reflecting the effects of medical interventions on morbidity as well as the length of life. Analyses that incorporate quality of life adjustment are sometimes categorized as "cost-utility" analyses.

The measurement, estimation, and valuation of the elements contained in a cost-effectiveness analysis is a complex undertaking. Chapter ii provides detail on the issues related to assessing the effect of interventions. The assessment of cost can be equally difficult. Issues include the management of indirect costs, such as hospital overhead the identification of costs as distinct from charges, which often contain elements of profit or costs shifted among patients and the generalizability of costs from one practice or region to other areas. The measurement of quality of life is also complex and has developed into a specialized field of study. 4

Contexts for the Use of Cost-Effectiveness Analysis: Societal and Clinical

Cost-effectiveness analysis frequently takes a "societal" view in analyzing health care interventions. Although there is no single "societal" decision maker, various organizations and individuals make decisions that do or should reflect a range of societal goals. Public and private health insurance systems, hospitals and other providers, and government advisory and regulatory bodies set policies and develop recommendations that influence or determine aspects of clinical practice.

The standard argument for the use of cost-effectiveness analysis in these contexts is the need to allocate resources efficiently, obtaining the most desirable set of services for a given budgetary outlay. This objective should be distinguished from that of saving money -- a purpose often incorrectly ascribed to cost-effectiveness analysis. 5 Although cost-effectiveness analysis is seldom used in the textbook fashion of ranking interventions and selecting the most cost-effective set, it can offer important guidance to decision makers. It can be used to screen out new procedures or technologies that are poor uses of medical resources. It can illuminate the trade-offs involved in service delivery, such as by outlining the costs and returns for more frequent screening or for applying certain treatments or preventive interventions to particular population groups.

As interest in prioritizing uses of health care resources increases, a range of public and private efforts is focusing on the development and refinement of practical cost-effectiveness applications. Several countries are developing systems for incorporating cost-effectiveness analysis into decisions whether to include drugs in government formularies or for marketing approval.6,7 In 1993, the World Bank introduced the disability adjusted life year (DALY) in its World Development Report: Investing in Health, spurring interest in the use of cost-effectiveness criteria for allocating health care resources in developing countries. 8

The clinical setting is clearly a primary location for the implementation of policies guided by cost-effectiveness analysis, but its use in this setting is controversial. Medical care policies, including those based on cost-effectiveness considerations, have the potential to constrain the clinician's traditional freedom to select among treatment alternatives. Debate also arises from the primacy of the clinician's advocacy role, which could be jeopardized if the clinician were charged with making decisions to achieve societal priorities that conflict with individual patient choices.

The degree to which the clinician can or should be responsive to general societal welfare as against individual concerns is likely to remain a topic of debate for some time. However, it is both reasonable and necessary for clinicians to consider cost-effectiveness in many cases, weighing whether the marginal benefit to an individual patient of a test, procedure, or treatment as compared to an alternative justifies its additional cost to the patient or to society as a whole.

Cost-Effectiveness Analysis as a Supplement to Information on Effectiveness

Cost-effectiveness analysis supplements information on effectiveness in two ways: by addressing the value of an intervention, and by clarifying and aggregating information related to effectiveness and cost. As noted earlier, it does not address all additional factors of interest to a decision maker. For example, neither an assessment of effectiveness nor of cost-effectiveness will address a policy's effect on the relative well-being of different socioeconomic groups, so-called "distributional equity" effects.

Value

Cost-effectiveness information can be used to assess whether an intervention is a "good buy" compared to others or to some formal or informal standard. The cost-effectiveness ratio is a form of price in this sense. More technically, the incremental cost-effectiveness ratio indicates the additional quantity of resources that must be devoted to an intervention, compared to a less expensive but less effective alternative, in order to obtain a given additional benefit. It thus demonstrates the opportunity cost -- the value of the foregone alternative use -- of the investment.

For example, if a prostate cancer screening program is implemented, the opportunity cost incurred is the health benefit that could have been obtained had the funds been spent on a different program. Cost-effectiveness analysis summarizes the costs per unit of benefit for comparison with the alternatives, or simply for making a judgment about the overall "price" of the program's benefits.

In the clinical setting, the opportunity costs of clinicians' time and other resources are also relevant for the setting of priorities. Limits to such requisites as office space, the duration of the office visit, and the patient's ability to assimilate medical advice during a given visit are particularly evident for interventions such as counseling and patient teaching. To maximize the value of the visit to the patient, the clinician must consider the opportunity cost of various uses of the available resources and prioritize the interventions to be included.

A primary component of value is the magnitude of the benefit offered by an intervention. To be desirable, an intervention must be more than effective its effect must be important enough to justify the risks and costs associated with it. An effective intervention may be clinically inconsequential, or it may help so few of the individuals to whom it is offered that it is not worth implementing. Cost-effectiveness analysis provides an insight to the magnitude of the benefit an intervention provides. Frequently, analyses report the magnitude of the benefit directly. In almost all cases, however, the cost-effectiveness ratio provides an indirect indication. If it imposes any meaningful cost, an intervention with minimal effectiveness will have a very high ratio of cost to effectiveness, alerting the decision maker to the need to examine the desirability of the intervention.

Aggregation of Effects

The ability of cost-effectiveness models to account for a wide range of an intervention's effects offers a particular advantage to decision makers in determining the value of a service. The full effect of health care policy decisions is difficult to assess intuitively, involving benefits and costs that accrue to different persons or groups and occur at different times. Cost-effectiveness analysis offers a systematic approach to documenting and aggregating these effects.

Cost-Effectiveness Analysis and Recommendations for Clinical Preventive Services

Cost-effectiveness analysis has direct relevance for policies concerning clinical preventive services. An example is that of screening and vaccination to prevent the complications of rubella during pregnancy (see Chapter 32). On the basis of evidence of rubella vaccine effectiveness, the Task Force recommends screening all women of childbearing age and vaccinating susceptible women or, alternatively, routine vaccination of all women in this age group.

Should this recommendation be implemented? If so, under what protocol? Preventable rubella cases occur an average of 7 cases of congenital rubella syndrome occurred in the U.S. each year during the 1980s, and a larger number during the rubella outbreak in the early 1990s. 9 Screening and vaccination strategies could likely prevent some cases, although not all, in upcoming years.

From a broad perspective, the relevant issue is the opportunity cost of implementing this effort. If the resources available for health services were unlimited, there would be no opportunity cost and no reason to question the implementation of rubella vaccination for women of childbearing age. In fact, more intensive strategies than those the Task Force recommends, such as repeated vaccination of adult women, might be an even surer way of eliminating as many cases of rubella in pregnancy as possible. Because the level of health care spending by business, government, health care institutions, and individuals ultimately affects quality of life both directly and indirectly, however, it becomes necessary to assess whether the benefit of an intervention like rubella vaccination of adult women -- or of one vaccination protocol versus another -- is worth its cost.

On its face, the case of rubella vaccination prompts several questions related to cost-effectiveness. The total cost of fully implementing the Task Force recommendation would be significant because of the large population involved: some 60 million women aged 15 to 44. In addition, the attainable benefit is limited by the low incidence of preventable rubella in pregnancy. Childhood vaccination has already markedly decreased the overall incidence of the disease, and benefit is further limited in the case of a screening strategy by the occurrence of rubella infection in women with apparent immunity on screening. 10 Finally, if a rubella vaccination policy were to be implemented, a strategy or protocol would need to be chosen. Routine vaccination is presumably more effective but may be more costly than screening followed by selective vaccination. Would the added benefit justify the difference in cost?

Similar issues arise in considering many of the clinical preventive services discussed in this volume. The recommended screening of all persons over age 50 for colorectal cancer (see Chapter 8) would potentially add billions of dollars to health system costs and should be considered in light of the benefit it could provide. 11 Recommended counseling interventions for young adults would compete for time during office visits and should be prioritized in terms of their demands on practitioner and patient time and the benefit they offer. Recommended protocols -- the frequency of interventions and the populations targeted to receive them -- can greatly affect the outcomes and costs of an intervention and should be determined with regard for cost-effectiveness considerations.

In general, the policy questions regarding these interventions do not concern their inherent desirability. The effectiveness and risks of interventions recommended by the Task Force have been carefully evaluated. Instead, the question is whether there are likely to be other interventions that are more desirable -- other uses of resources that are preferable. While the opportunity cost of a given service often is not apparent, the overall pressure of resource constraints in all domains of health care is becoming increasingly obvious. In many areas of medical technology, large additional expenditures have been shown to produce only small, marginal gains in health status or outcome at our current levels of health care technology.

Use of Cost-Effectiveness Analysis in the Absence of Data on Effectiveness

Evidence of effectiveness, although always desirable, is not always available. Research documenting effectiveness is frequently complex, time-consuming, and expensive. As a result, the effectiveness of many services remains to be established. For others, evidence of effectiveness is equivocal. Cost-effectiveness analysis cannot provide evidence of effectiveness where none exists. However, it can distinguish critical gaps in existing knowledge from questions that are less important for future research because a decision is not influenced by the existing uncertainty. Cost-effectiveness analysis can also illuminate dimensions of the trade-off between action and inaction.

For example, the Task Force has found insufficient evidence to recommend for or against providers counseling their patients to engage in physical activity (see Chapter 55). Cost-effectiveness analysis could summarize the conflicting considerations entering into a decision on this intervention, including the implications of both a decision to implement and not to implement exercise counseling.

In general, the decision to provide a service that has not been proven effective must consider the extent of potential benefit, the likelihood that the intervention is effective, and the type of evidence indicating probable effectiveness. These decisions must also weigh the costs and untoward effects of the intervention, including the societal costs of institutionalizing an unproven practice. Because of the possibility for harm and the cost, the provision of an unproven intervention to an asymptomatic and healthy population is seldom justified. When a probablyeffective intervention imposes little or no cost and is safe, its implementation may be warranted.

Cost-Effectiveness of Preventive versus Curative Services

Prevention is still commonly promoted on the basis of claims that it saves money, although screening, counseling, and other preventive services often cost more than they save, just as other medical services do. Given this tendency, efforts to document the cost-effectiveness of preventive measures may be interpreted to imply that the value of preventive services should be examined closely, while curative services are subjected to no such test.

Preventive and curative services should be held to the same basic standard of cost-effectiveness. A preventive service may be more cost-effective than many curative services and be a good use of health care funds, even if it is not as cost-effective as other preventive services.

Current Limits on Use of Cost-Effectiveness Analysis

Cost-effectiveness studies are currently available on many health care services. The weight of the cost-effectiveness evidence is convincing for a limited number of these, most of which are clearly cost-effective or clearly cost-ineffective in any realistic scenario.

A much larger group of services remains for which cost-effectiveness is not yet established. Information on costs and outcomes is inadequate for many interventions. For others, the cost-effectiveness analyses have not been done, or their quality is insufficient to provide conclusive evidence. Finally, the variation in cost-effectiveness analysis methodology often makes it difficult to take cost-effectiveness results at face value.

Decision makers today should consider cost-effectiveness results where adequate analysis has been done. Care should be taken in evaluating the methodology used. The reader should examine challenges to the study's validity, such as the choice of costs included in the analysis and the quality and representativeness of data on costs and effectiveness. In addition to providing specific information, cost-effectiveness analysis raises important questions about the opportunity costs of alternative choices that decision-makers should consider.

Cost-Effectiveness and Task Force Recommendations on Effectiveness

The Task Force recommendations in this Guidereflect the evidence of effectiveness of interventions. They are intended to inform clinicians about a basic and important aspect of clinical preventive services and contribute to the process of evaluating the priority of these services. The recommendations do not systematically incorporate other decision factors, such as cost-effectiveness or the ethical implications of recommendations, and therefore should not be viewed as comprehensive societal guidelines for clinical preventive services. Evidence of effectiveness should be supplemented when possible by information on cost-effectiveness in any decisionmaking context in which available resources can be used for multiple purposes.

The draft of this chapter was prepared for the U.S. Preventive Services Task Force by Joanna E. Siegel, ScD, and Donald M. Berwick, MD, MPP.

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