Are Whole-Body Scans Useful as a Screening Tool?

Richard Dehn, MPA, PA-C

Disclosures

October 16, 2002

Question

Whole-body scans are being heavily advertised. What are the pros and cons of these scans in terms of overall healthcare/disease detection, as compared to currently recommended screening methods?

Harold Fruchter, PA-C

Response from Richard Dehn, MPA, PA-C

Over the last century American medicine has been able to deliver remarkable improvements in individual health. This has been as a result of improved nutrition and exercise, the development of more effective treatments for many diseases, the success of disease-specific screening processes (such as Pap smears or screening for hypertension and diabetes), and the result of individuals taking more responsibility for their health.[1]

Whole-body scans are attractive to patients because they invoke the idea that individual patients can obtain a convenient screening test that will detect serious diseases early or provide reassurance that they are disease-free. This appeal has stimulated a recent trend toward the use of scanning services marketed directly to patients seeking disease prevention screening. Out-of-pocket costs for these range from $300 for a lung scan to around $1000 for a whole-body scan.[2] Typically these screening processes involve computed tomography (CT ) scanning technology, with the whole-body variety scanning from the neck to the pelvis.[3] So why are so many in the medical community strongly opposed to patients using whole-body scanning to take charge of their own health?[4]

To understand arguments against the use of CT scanning for disease screening, it is useful to review the characteristics of a good screening process.[5] First of all, a screening tool should be good at detecting a disease or condition in which early detection would make a difference in the outcome. While early detection may be important in the treatment of some diseases, for other diseases early detection is not helpful in improving outcome, and thus is not considered worthwhile.

Screening is also most appropriate when the prevalence of a disease is high enough in the screened population to make the process cost-effective. Typically, it is not worthwhile to screen large populations for a rare disease. However, sometimes screening for rare diseases is justifiable when early detection using a cheap screening process will prevent grave, irreversible consequences, such as with congenital hypothyroidism. An ideal screening process will employ a relative cheap test that has good sensitivity (the ability of a test to detect disease when that disease is present) and good specificity (the ability of a test to accurately determine who doesn't have the disease in question). It is also important that a screening process not have harmful side effects.

The fact that whole-body scans are not aimed at screening for one specific disease makes it hard to determine the prevalence of the diseases for which the population is being screened. This in turn makes it difficult to determine how effective the scan actually is as a screening tool. What consumers want from whole-body scanning is a test that effectively identifies who is healthy and who is not, but there are no data to answer this simple question. Given the unknown sensitivity of whole-body scans for detecting treatable disease, as well as the recognized tendency of CT scanning to produce false positives (low specificity), it becomes impossible to determine how effective the technique is for screening treatable disease in healthy populations.

Whole-body scanning can lead to 2 types of misdiagnosis: (1) not diagnosing treatable disease that is present and (2) the detection of disease that is not present. The first example is possible since CT scan does not detect many common treatable diseases, such as hypertension and diabetes, that may be present in individuals who may use whole-body scans as a substitute for more comprehensive medical care. However, it is more likely that whole-body scanning could cause havoc by producing findings that require further investigation with more invasive and expensive processes, and that many of these subsequent investigations will identify benign conditions.[6] Since most whole-body scanning is performed without contrast, these are less effective than contrast studies in detecting some lesions and can make it difficult to distinguish whether lesions are benign. In turn, this may lead to further testing to make this determination.[1] Another important variable is where the screening standard, or cut-off, is set to distinguish a normal from an abnormal scan. Since all scans involve human interpretation of processes that are often benign, setting too low a threshold for interpreting a scan as abnormal will result in excessive false negatives, while setting it too high will miss pathology.[7] Both of these errors can be costly.

Additionally, radiation exposure from CT scans should be taken into account, since a whole-body scan will expose the patient to a dose of radiation equivalent to 500 chest x-rays.[8] When a symptomatic patient undergoes a CT scan, the risk of exposure is factored into the risks associated with the symptoms. However, in using the whole-body scan as a screening tool, exposing healthy patients to this level of radiation may not be justifiable in the absence of data indicating that this type of screening improves outcomes.

Since we don't know much about the effectiveness of using whole-body scans to screen for disease in asymptomatic individuals, it is easy to understand why third-party payers are reluctant to reimburse for these tests. Third-party payers know that making the testing more available will lead to a substantial increase in the number of patients being subjected to medical work-ups to separate real disease from the false positives. Since many of the findings from CT scan will require invasive processes for definitive diagnosis, many patients without disease will suffer iatrogenic consequences.

The financial burden of these additional work-ups would be substantial. One whole-body scan practitioner estimates that about 22% of patients exhibit a significant abnormality on whole-body CT screening.[9] If a substantial proportion of these patients with abnormal whole-body scans does not have treatable disease, this translates into a large number of patients that will undergo evaluations without improving their health. Even with whole-body scanning funded entirely out-of-pocket, the process currently can add to healthcare costs because most abnormal findings are evaluated within the traditional medical system, where third-party payers bear a substantial portion of the costs.

Currently, several organizations oppose the use of whole-body scanning as a disease-screening process in healthy individuals. These include the American College of Radiology,[10] the United States Food and Drug Administration,[6] and the American Association of Physicists in Medicine.[11] These organizations oppose the use of whole-body scanning primarily because they believe that it subjects patients to unnecessary radiation without documented scientific proof that the technique is effective in screening for treatable disease.

As scanning technologies improve and more data are obtained on their effectiveness, it is possible, in fact likely, that whole-body scanning technology will eventually be used for screening asymptomatic patients. Some experts think that magnetic resonance imaging (MRI) technology holds more promise than CT for use as a screening tool because MRI doesn't have the inherent radiation exposure risks of CT and may provide better sensitivity and specificity.[12]

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