The use of x-ray computed tomography (CT) for screening presents a paradoxical challenge to American health care consumers. The extraordinary spatial sensitivity of CT would seem to promise earlier disease detection and improved patient outcomes, but there are characteristics of the technology, the diseases at which CT screening is directed, and our health care financing system that complicate our ability to use CT effectively for this purpose.
To see why this is the case, it is necessary to first consider what is meant by the term "screening," Screening is the systematic testing of individuals who are asymptomatic with respect to some target condition. The goal of screening is to prevent, interrupt, or delay the development of advanced disease in the subset of the screening population that has a pre-clinical form of the target disease (unpublished report of the American College of Radiology, Methods Subcommittee of the Task Force on Screening Technologies). It follows, then, that there are some essential requirements for successful screening. First, screening must advance the time of diagnosis relative to that for individuals who have the condition and do not undergo screening. With screening, the disease is identified in the preclin-ical presymptomatic phase. While this is necessary, it is not sufficient. Second, there must also be a treatment available that is more effective for presymptomatic disease than for symptomatic disease�one that incurs less morbidity and results in a better health outcome. Finally, from a societal perspective, screening must produce greater benefit than it does harm, and it must do so at a cost that society can afford in the context of other demands on its resources. The question is whether these qualifications are fulfilled with respect to CT screening.
During the past several years, CT screening has been popularized in the media. It has been marketed by a small number of "technology leaders," and it is being adopted by an increasing number of radiologists and entrepreneurs. As a result, an increasing number of CT screening examinations are being performed nationally. All of this is occurring with little or no data to support the practice. It also is happening without third-party reimbursement. This means that individuals who seek CT screening are paying out of pocket for their examinations. Is there anything wrong with this? I believe most Americans subscribe to the belief that the individual has the right to spend his or her discretionary income according to preference. I also think, however, that they would agree to this only with the corollary that the individual who makes the expenditure should not only derive benefit from the purchase but should also assume any associated personal or financial risk or harm.
This is not the case with CT screening. While the individual makes the payment for screening out of his or her own resources, all subsequent screening-related costs that follow on as a result of indeterminate or positive findings are paid by public or private health insurance. As I will discuss later, these "follow-on" costs dwarf the initial screening expenditure. The fundamental economic problem with screening is what economists call "moral hazard." Patients neither know nor for the most part care about their health care costs because they are protected with third-party
insurance from the financial consequences of seeking medical care. Thus, the decision of an individual to seek screening may result in serious financial consequences for society in the form of higher expenditures for public insurance (Medicare and Medic-aid) and higher costs for employer-based health insurance.