Article Text

Evaluation of studies of health economics
1. Patricia W Stone, RN, PhD1,
2. Suzanne Bakken, RN, DNSc, FAAN1,
3. Christine R Curran, RN, PhD, CNA2,
4. Patricia H Walker, RN, PhD, FAAN3
1. 1Columbia University  New York, New York, USA
2. 2The Ohio State University and Medical Center  Columbus, Ohio, USA
3. 3Graduate School of Nursing  Uniformed Services University of the Health Sciences  Bethesda, Maryland, USA

A rural hospital hires a new infection control professional, EL, who has just received her master’s degree and trained in infection control departments that were up to date on the best evidence. EL reviews the infection control policies and learns that traditional central line catheters are used. Where she trained, a new, more expensive, antiseptic catheter was used. The new catheter is impregnated with chlorhexidine and silver sulfadiazine and costs $25 more than the traditional catheter. Because the new catheter is designed to reduce the incidence of hospital associated infections, particularly blood stream infections that are catheter related, EL recommends that the hospital begin using it in place of the traditional central line catheter. However, hospital administration and the purchasing department question the value of this new, more expensive, antiseptic impregnated catheter. Issues related to both cost and the possibility of improved outcomes are discussed at a meeting with intensive care nurses, physicians, and representatives from hospital administration and the purchasing department. Specifically, the questions are: (1) is the antiseptic impregnated catheter economically efficient? In other words, are the additional costs of the catheter offset by potential cost savings in reduced number of infections, which will affect length of stay? (2) Is the antiseptic impregnated catheter more cost effective when used in certain types of patients (eg, patients at high risk of catheter related infections, such as immunosuppressed patients)? An interdisciplinary team is asked to conduct a literature search and make an evidence-based recommendation. ## Introduction As healthcare technology continues to expand, the cost of using all effective clinical services exceeds available resources. Because of the scarcity of resources, decisions regarding the implementation of new services frequently need to be based on economic analysis. Economic analysis is a set of formal, quantitative methods used to compare 2 or more treatments, programmes, or strategies with respect to their use of resources and their expected outcomes.1 Economic evidence seeks to inform resource allocation decisions at different levels, including institutions (eg, hospitals) and regional or national governments. Unfortunately, not all economic evidence is of high quality. To identify scientifically sound evidence that can inform nursing related resource allocation decisions, nurses need to evaluate the research by answering the questions outlined in Table 1. These questions will be discussed and illustrated with examples of interest to nurses; then, the clinical scenario will be addressed and a published economic evaluation will be critiqued to further illustrate these points. Table 1 Questions to help critically appraise economic evidence ## Are the results of this economic evaluation valid? The number of published economic evaluations is growing.2 However, many experts in the field have questioned the methodological rigour of these evaluations.3,4 Therefore, it is important for nurses to be able to assess the validity of the methods used in these economic studies in order to determine which findings they will apply to their setting. All rigorous economic evaluations consider the opportunity cost; that is, the value of the benefits foregone in alternative uses when a resource is used for a given purpose.5 For example, the opportunity cost to a municipality’s health department of funding a community health screening programme for the elderly may be the foregone benefits of not being able to fund a prenatal programme for at risk pregnant women. In addition, economic evaluations should consider the extra (ie, incremental) benefit that would be gained for the extra (ie, incremental) cost. A classic example illustrating incremental cost and effectiveness is the sixth stool guaiac test used to screen for colorectal cancer in people over 40 years of age. In the US, the average cost per case of cancer detected using ≤5 tests has been calculated to be US$2541, but the incremental cost of the sixth test was estimated to range between $47 and$127 million.6 This is because the probability of detecting an additional case of cancer (the incremental effectiveness) is so low that millions of dollars (the incremental costs) would be spent before identifying one more person with cancer.

### IS THE APPROPRIATE ECONOMIC EVALUATION METHOD USED?

5 different analytic tools are commonly used to assess the economic effects of new and established healthcare interventions (Table 2). Each method will be discussed below. The costs should be measured the same in all analyses, but the methods differ in how effects or outcomes are measured.

Table 2

5 types of economic evaluations

## Will the results help me in caring for patients?

The applicability or generalisability of the results to your own setting needs to be considered. In an economic evaluation, the applicability of both the costs and effectiveness are assessed.

### DO THE COSTS IN THE REPORT APPLY IN MY OWN SETTING?

Costs may vary because of local prices and different practice patterns. The sensitivity analysis should cover a range of costs that may account for such differences.

### WILL THE INTERVENTION (OR NEW MODEL OF CARE) BE EFFECTIVE IN MY SETTING?

As always, you need to consider how your patients are similar to or different from those in the study. You also need to assess your patients’ preferences for the outcomes and utilities used in the analysis.

## The search

The interdisciplinary team charged with reviewing the literature on the new antiseptic impregnated catheter, searched Medline, the NHS Economic Evaluation Database, and the Health Technology Assessment Database (the latter 2 are part of the Cochrane Library) using the terms costs, central lines, and catheter related infection. The study thought best to answer the question is summarised in Table 4.

Table 4

Summary of an economic analysis on central line catheters and catheter related blood stream infection (CRBSI)

Veenstra et al assessed the cost effectiveness of short term use (2–10 d) of a standard multilumen central venous catheter compared with a catheter impregnated with chlorhexidine silver sulfadiazine for a hypothetical cohort of patients at high risk for catheter related infections.31 The economic evaluation method chosen, CEA, was appropriate for the question. The 2 alternative interventions were well defined and appropriate costs for each of the alternatives were considered in the analysis. Direct medical costs were measured in 1998 dollars and included costs related to incremental length of stay in the ICU and ward for management of catheter related bloodstream infections, hypersensitivity reactions, and locally infected catheter insertion sites.

The probabilities of clinical events were well documented. Probabilities for catheter related bloodstream infections and catheter colonisation were based on summary risk ratios calculated from a meta-analysis of 13 RCTs that compared outcomes for antiseptic impregnated catheters with standard central venous catheters. This meta-analysis included results from clinical trials in which most patients were at high risk (such as patients in ICUs or with immunosuppression). Probability of death attributable to catheter related bloodstream infections was based on reports in the literature. The authors found no reported cases of hypersensitivity to chlorhexidine silver sulfadiazine impregnated central venous catheters in the US, so they used rates from Japan. The analysis showed that antiseptic impregnated central venous catheters had greater efficacy and lower costs than standard catheters. These results remained consistent through an appropriate series of multivariate and univariate sensitivity analyses.

Although this study does not allow us to answer our first question about the total population of hospital patients requiring catheters, it does inform clinical decision making related to patients at high risk of catheter related infection. We have learned through appraisal of a high quality study that antiseptic impregnated central venous catheters are cost effective in high risk patients. Based on this economic evidence, the interdisciplinary team recommends use of the new catheters in their ICUs but not throughout the hospital until further studies are done.

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