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Ann Thorac Surg 2004;78:1534-1535
© 2004 The Society of Thoracic Surgeons
Division of Cardiothoracic and Vascular Surgery, University of Kentucky, C208, UKMC800 Rose St, Lexington, KY 40536, USA
ferraris{at}earthlink.net
The article by Nilsson and coworkers claims that the EuroSCORE (a popular mortality risk scoring system used extensively in Europe) is also useful for predicting resource utilization in cardiac surgical patients. This work deserves comment in three areas.
First, there are some quirks about the authors' measurements that need to be pointed out. The authors use log transformation of the dependent variable (hospital cost) in order to measure the relationship of EuroSCORE to hospital costs. Their Figure 2 shows a very linear regression between cost and EuroSCORE, only after the cost data are log transformed. The advantage of log transformation is that the influence of outliers is minimized and the regression coefficient looks better. The disadvantage is that the resulting regression line using log transformed data are always more linear than nonlog transformed data and gives an inflated sense of dependence of the outcome variable (cost) on the predictor variable (EuroSCORE). It would be wishful thinking to suppose that the EuroSCORE predicts hospital cost without significant variability. In fact, the authors acknowledge that the EuroSCORE is not a useful measure of hospital costs for individual patients because of this variability. Other measurement issues that are a little quirky include the way that hospital costs were measured by the authors. This method of cost calculation is unlikely to be duplicated by any other center in the world. The cost calculation uses factors like the Lund ICU workload score and the "Starting CostOp," which is a factor estimated by the hospital accounting system (see their Table 2). This idiosyncratic estimate of cost is unlikely to be duplicated by other institutions that may wish to copy the authors' methods. In addition, the authors chose to exclude operative deaths from their analysis. We found that the most costly patients who undergo cardiac operations are those who die from the operation [1]. It may be that exclusion of the intraoperative deaths omits important information about determinants of hospital costs. For these reasons, the prediction model of hospital costs by Nilsson and coworkers is neither transferable nor robust.
Second, each of the reviewers of this article asked a similar question (ie, What is the clinical usefulness of the cost prediction model based on the EuroSCORE for the individual patient?). The short answer to this question is that prediction of costs for individual patients by this system is inaccurate and the EuroSCORE should not be used for this purpose. The authors acknowledge this shortcoming and recognize that other investigators have not been able to apply models of risk-adjusted cost to individual patients, only to larger patient cohorts [2, 3]. They did find some correlation of the EuroSCORE with weekly costs in certain patient cohorts. They suggest a novel use of the EuroSCORE, namely, predicting weekly intensive care unit costs in certain patient cohorts. This may allow week-to-week assessment of resource needs in the intensive care unit or operating room based on the risk profile of patients being operated upon during a given week. This is an intriguing possibility and should be tested in larger cohorts.
Third, if the EuroSCORE can not be used to predict individual patient costs and the authors' means of measuring hospital costs are quirky, then what is the value of this analysis? The answer lies in the assessment of what a health care payer must pay to treat patients. In the United States, the Leapfrog Group (Washington, D.C.) and other consortiums of health care payers are concerned about the spiraling increase in health care costs and ultimately the cost that corporations must pay to provide health care to their beneficiaries. By default, and because there is not really a good measure of hospital (and individual provider) quality that is readily understood by corporate executives and beneficiaries, these consortiums have chosen provider volume as a surrogate for quality. These same consortiums assume (without much justification) that high quality will translate into lower costs. The problem with using hospital volume as an indicator of quality and ultimately lower health care costs is that volume alone is a poor indicator of both quality and cost [4]. Some high-volume providers have poor outcomes or high costs and some low-volume providers have good outcomes or low costs. It seems so obvious that volume is a poor indicator of quality, but the consortiums that worry about health care costs are at a loss to find a better indicator of quality than hospital (or provider) volume. Herein lies the potential of studies like that of Nilsson and coworkers. The EuroSCORE is a far better predictor of cost than hospital volume. The score is easy to apply and provides a more accurate way to compare providers than simple hospital volume. Is the EuroSCORE the best indicator of hospital cost? It probably is not. However, studies like that of Nilsson and coworkers are the first steps in predicting the costs and the value of services provided by hospitals and individual practitioners. We can only hope that corporate executives and members of the Leapfrog Group will read this article and tip them to the fact that there are better indicators of quality than hospital volume.
References
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