TO THE EDITOR:
In "The Utility of Histological Examination of Tissue Removed during Elective Joint Replacement. A Preliminary Assessment" (80-A: 331—335, March 1998), by Raab et al., the authors referred to their study as both a cost-effectiveness analysis (p. 331) and a cost-benefit analysis (p. 335). However, this study is neither a cost-effectiveness analysis nor a cost-benefit analysis; it is a cost-identification study. This distinction is important.
There are three different types of economic analyses: cost-identification, cost-effectiveness, and cost-benefit3. One uses cost-identification analysis to estimate the cost of an intervention but not its benefit. A cost-effectiveness analysis has a broader perspective in that it incorporates both cost and effect. The cost and the outcome (or benefit), however, are not expressed in the same units. For example, the cost is expressed in dollars and the outcome is expressed in years of life gained (quality-adjusted life-years). The results of this type of analysis are meaningful only in comparison with those associated with other interventions. Such comparison is essential in order to establish if the cost of life saved is expensive or inexpensive, depending on how else the money could have been spent. Finally, in a cost-benefit analysis, both the cost and the outcome are considered and both are reported in monetary terms. Therefore, the benefit must be converted into monetary units and then the cost can be subtracted from the benefit to determine the value.
In the study by Raab et al., the cost of histological examination of tissue removed during 168 elective joint replacements was determined to be $10,698.24. The results were then reported as the cost per discrepant diagnosis ($668.64) and the cost per discordant diagnosis ($10,698.24). These outcomes (discrepant and discordant diagnoses) have no meaning in any other context; therefore, this information cannot be used to determine economic health-care policy. In addition, decisions based on cost-effectiveness are always relative to the alternative choices, which were not presented.
A proper cost-effectiveness analysis requires conversion of the outcome information to an outcome, such as quality-adjusted life-years4, that facilitates comparison with other health services. For example, the cost-effectiveness of histological examination (and the quality-adjusted life-years gained) could be compared with the cost-effectiveness of no histological examination (no quality-adjusted life-years gained). In this study, the quality-adjusted life-years gained would have to be calculated for the discrepant and discordant diagnoses and the resulting patient outcomes. Health-care policy can be determined only after all costs and benefits, and the potential alternatives, have been considered.
Kevin B. Freedman, M.D.: Department of Orthopaedic Surgery, Center for Clinical Epidemiology and Biostatics, University of Pennsylvania School of Medicine, 2 Silverstein Pavilion, 3400 Spruce Street, Philadelphia, Pennsylvania 19104-4283
Dr. Raab, Dr. Slagel, and Dr. Robinson reply:
We thank Dr. Freedman for providing a brief textbook description of the different types of economic analyses. We agree that the distinction among the terms cost-benefit, cost-effectiveness, and cost-identification is important, although cost-analysis experts may disagree about particular usage. We take issue with Dr. Freedman's belief that the outcomes of discrepant or discordant diagnoses "have no meaning in any other context" and "cannot be used to determine economic health-care policy." The histological examination produces information that may or may not yield a postoperative impression that is different from the preoperative impression. If the histological examination never yielded any information other than what was expected clinically or never affected patient care, then it would not be needed. There has been little study of how some histological diagnoses actually are used in patient care. The outcomes associated with discrepant or discordant diagnoses were chosen as the benefit of the histological examination precisely to serve as a starting point. We agree that additional studies are necessary to explore how discrepant or discordant diagnoses affect patient care and that the measurement of such things as quality-adjusted life-years gained may be important. However, if the histological diagnosis never affected quality-adjusted life-years (as evidenced by never affecting the management of the patient or the outcome), then it would not be necessary to measure quality-adjusted years. Dr. Freedman's last sentence regarding the determination of health-care policy is idealistic yet somewhat naive. Health-care policies already exist and were not and will not be determined by the measurement of all costs and benefits, which is probably an impossibility. We are not aware of any studies that have shown that the histological examination of tissues removed during elective joint replacement is cost-effective. If policy is to be based partly or completely on cost-effective measures, then there is no rationale to support the continuation of the histological examination.
We also would like to make several comments regarding the Editorial by Bullough and Dorfman that accompanied our manuscript1. We infer from that Editorial that to not perform histological examination is to be against "scientific medicine." Bullough and Dorfman did not take issue with our manuscript on scientific grounds but rather cited an abstract2 that they believed supports the continuation of the histological examination of joint tissues and concluded that the case is closed. We agree with Bullough and Dorfman that the issues of quality control and quality assurance are important, and we stated in our manuscript that we did not intend to investigate these issues. There are other ways to address these issues than to examine all specimens histologically. We concur that the histological examination of tissue removed during elective joint replacement provides information that potentially could be used in many ways. However, we believe there is a limit to what we can and should do to obtain this information. For example, should we examine the entire joint histologically rather than just submit a few sections in order to obtain more information? We do not know of any pathologist who would advocate this practice. The policy of examining all joint tissues histologically is based mostly on anecdotal evidence; is not uniformly practiced by all pathologists; and, we believe, should not be continued on the basis of unsupported claims of quality management and so-called knowledge gained. These issues need additional study, and the measurement of outcomes, such as quality and cost, will continue to investigated by medical scientists.
Stephen S. Raab, M. D.: Department of Pathology and Laboratory Medicine, Allegheny University of Health Sciences, Allegheny General Hospital, 320 East North Avenue, Pittsburgh, Pennsylvania 15212-4772
Daniel D. Slagel, M.D.: Department of Pathology, St. Mary's Hospital, 2635 North 7th Street, Grand Junction, Colorado 81502-1628
Robert A. Robinson, M.D., Ph.D.: Department of Pathology, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, 5216 RCP, Iowa City, Iowa 52242-1009