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12. Economic Evaluation in Infection Control |
Introduction Healthcare costs are rising and decision-makers are increasingly relying on both clinical effectiveness and economic efficiency when making healthcare decisions. There is sound rationale for economic analysis: resources are scarce and choices must be made on how to use them. The traditional factors addressed during the evaluation of new interventions include safety (are the side effects acceptable?), efficacy ( can it work?), and effectiveness ( does it work?). The economics-based term, “efficiency” should be considered when judging the worth of a new intervention. Efficiency of an intervention helps answer whether or not the additional cost of an intervention is worth the additional benefit. There are several different types of economic analysis that can be employed, including cost minimization, cost effectiveness, cost benefit, and cost utility analysis. Cost minimization (identifying the least costly alternative that leads to an equivalent outcome) is rarely used because the clinical consequences of different interventions are rarely equivalent. Cost benefit analysis (placing a monetary value on both the costs and the benefits) is also used rarely because it is difficult to place a monetary value on states of health. Cost utility analyses are useful when there are no expected mortality differences between interventions, only differences in physical well-being which can be expressed as quality adjusted life years (QALY). Cost-Effectiveness Analysis A cost-effectiveness analysis quantifies the trade-off between increased healthcare expenditure and improved healthcare outcome and measures the cost required to achieve a given clinical benefit. An example would be the assessment of an intervention to reduce catheter-related bloodstream infection using antiseptic-coated vascular catheters. The cost of the antiseptic catheter is usually more than the standard catheter, however this can be compared with the clinical benefits associated with the antiseptic catheter. Thus, a cost-effectiveness ratio can be generated. It is the total dollars spent for the intervention divided by the number of cases of catheter-related bloodstream infection prevented. If the antiseptic catheter produced superior benefits at an increased cost, then an incremental cost-effectiveness ratio – the amount of money needed to produce an additional clinical benefit – could be calculated. However, if the intervention led to an actual reduction in overall costs while improving health outcomes, it would be called a “dominant” intervention, since it would provide both clinical and economic benefits. Table 12.1 helps decide when a cost-effectiveness analysis is appropriate. In general, there are four possibilities when comparing two interventions, A and B. The first possibility is that A is more effective and costs less. Thus, A is the dominant strategy and should be used without further analysis. Likewise, when B is more effective and costs less than A, B is dominant and a cost-effectiveness analysis is unnecessary. However, as is more common, when A is more effective than B but costs more than B, it is helpful to perform an incremental cost-effectiveness analysis to quantify the clinical and economic consequences of intervention A. Examples of such analyses would include antiseptic-coated vascular catheters to prevent catheter-related bloodstream infection [1] or silver alloy urinary catheters to prevent urinary catheter-related infection [2]. Such studies have been performed and have found that the intervention is likely to be worthwhile in many circumstances. An incremental cost-effectiveness ratio is interpretable only when compared with another incremental cost-effectiveness ratio examining the same health outcome. For example, the cost-effectiveness of preventing local vascular catheter-related infection cannot be directly compared to the cost-effectiveness of preventing urinary catheter-related bacteremia. |
Table 12.1. Choosing among alternative interventions in a cost effectiveness analysis Back to text
COSTS |
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A<B |
A>B |
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| EFFECTS | A>B | A is Dominant |
Incremental (Cost-effectiveness analysis useful) |
| A<B | Incremental |
B is Dominant (Cost-effectiveness analysis unnecessary) |
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A = Intervention "A"; B = Intervention "B"
MEASURING EFFECTIVENESS AND COSTS Effectiveness and Cost Estimates Economic evaluations of health care interventions depend upon solid clinical evidence of effectiveness in order to establish benefits and risks. The validity of the clinical data is crucial to the overall usefulness of the analysis. Many economic evaluations rely on a single randomized trial or a single observational study to estimate clinical benefit. Some studies rely on less rigorous or non-scientific sources of information for outcome assessment, such as clinical opinion and expert panels. Estimates derived from large-scale, multi-center trials are widely considered the “gold standard,” however these data often are not available. In addition to effectiveness estimates, the analyst must also estimate the cost inputs. Often, however, cost is poorly defined for different infection control interventions as well as for the nosocomial or hospital acquired infection under consideration. Meta-analysis Meta-analysis is a “quantitative approach for systematically combining the results of previous research in order to arrive at conclusions about the body of research.” [3] Meta-analysis is used to statistically pool the results from individual studies, usually randomized trials, to obtain an estimate of the summary effect size across studies. The summary measure from a meta-analysis is often used to derive the probability of treatment success in a cost-effectiveness analysis [4]. Even if the benefit of an intervention could be demonstrated in every clinical setting, the cost-effectiveness ratios would vary considerably depending on local economics. Thus, an intervention that may appear “cost effective” in one country or hospital district (e.g., with a cost-effectiveness ratio less than $50,000 per life year saved), may be considered too expensive elsewhere. Economic evaluation in the area of infection control can be performed in a rigorous and straightforward manner, however several barriers exist to its routine introduction. First, since economic evaluation is not widespread in infection control, terminology must be used correctly. Often, when medical directors and other decision-makers say, “cost effective” they imply cost savings . However, “cost effective” technically indicates that we are spending an additional amount of money for an additional clinical benefit and is based on the explicit comparison of one strategy with another. Cost savings imply that we are getting an equivalent or greater clinical benefit and actually saving money; this scenario is rare. The cost-effectiveness of intervention A compared with intervention B can range from cost saving, cost neutral, cost effective to cost ineffective. Another important issue within infection control is that the attributable morbidity, mortality, and costs of nosocomial infection are difficult to assess. EVALUATING AN ECONOMIC ANALYSIS There are several important criteria by which economic analyses should be judged (summarized in Table 12.2) [5]. The first question is whether or not a well-defined research question was posed. This is of fundamental importance, since a research question that is not worth answering is usually not worth answering well. Second, it is important that all the legitimate and reasonable competing alternatives be evaluated in the analysis. Third, it is vital that the effectiveness of the intervention be clearly established, since an intervention that is not effective will certainly not be cost-effective. Finally, it is critical that all the important and relevant costs and consequences of the intervention are identified and considered, depending on the perspective of the analysis. |
Table 12.2. Questions that should be answered when performing
or reading a cost-effectiveness analysis Back to text
1. Was a well-defined question posed? |
2. Were all the competing alternatives evaluated? |
3. Was the effectiveness of the intervention established? |
4. Were all the important and relevant costs and consequences for each alternative identified (depending on the perspective)? |
5. Was uncertainty in the estimates adequately evaluated? |
References
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