Computed tomography (CT) scans are x-ray scans that use a computer to produce cross-sectional images of whatever part of the body is being studied. They can be used to examine the organs for signs of injury, tumors (cancerous and noncancerous), coronary artery disease , and certain other disorders.

In the past five years or so, the public has become more aware of the idea of using a whole-body CT scan for screening purposes. Screening tests ( Pap tests for cervical cancer are an example) are performed to detect disease before symptoms develop.

Whole-body CT screens, however, are much more controversial than tests such as the Pap test. People who support their use point out the benefits of early detection of cancer, for example. Opponents say that the monetary costs outweigh the potential benefits. There’s also a high risk of false-positive results, which mistakenly identify disease when none is present.

In a study published in the February 2005 issue of Radiology , scientists created a computer model to weigh the costs of whole-body CT screening plus any resulting follow-up procedures against any increase in life expectancy that resulted from the CT scan. They found that, on average, the whole-body CT screen increased life expectancy by only six days, at a cost of $2,513 per patient. In addition, out of every 1,000 people screened, 908 had at least one false-positive result that required further testing.

About the Study

The scientists created a computer model based on a hypothetical group of 500,000 men with no disease symptoms who were undergoing a onetime whole-body CT screening. They were compared to men who received routine care and no CT scan. The conditions considered for this study were: pancreatic , lung , liver , kidney , and colon cancer, abdominal aortic aneurysm , and coronary artery disease.

For the whole-body CT screening group, the model assigned diseases to each man according to their prevalence in the general male population. Then, based on the known sensitivity (ability of the test to correctly detect disease when it is present) and specificity (ability of the test to correctly identify the absence of disease when it is not present) of CT scans, the model determined whether the scan correctly identified each patient’s disease status.

The scientists assumed that cancers identified by the whole-body CT screen were found at an earlier stage than they would have been through routine care. Some men had more than one disease, so the researchers based life expectancy on the disease with the shortest expected survival time. For the purposes of this study, CT scans were assumed to cost $900, in 2001 US dollars.

The costs of the CT scan (and any follow up tests) and the increase in life expectancy that could be attributed to it were compared to the costs and outcomes for men receiving routine care.

The Findings

The researchers found that, on average, whole-body CT screening increased life expectancy by only six days at an additional cost of $2,513 per person, compared to men receiving routine care.

The CT screen also had a high false-positive rate; for every 1,000 men screened, the test detected at least one false-positive test result in 908 men. Additional testing and follow-up in patients with false-positive test results accounted for almost one-third of the total costs for the CT screened patients. Only 2% of the patients actually had disease.

This study had some limitations. First, models tend to oversimplify reality, and cannot be as accurate as results from clinical trials. In addition, the model assumed that earlier detection of disease would result in increased survival time, which is not necessarily true.

How Does This Affect You?

This study suggests that obtaining any benefit of whole-body CT screening for middle-aged men with no symptoms is extremely expensive. Of course, if consumers are willing to pay out of pocket for the scan, the decision is entirely up to them.

However, an important finding of this study is that follow-up testing resulting from false-positive CT results makes up a substantial proportion of the total costs. So even though whole-body CT screens are generally paid for by the consumers, health insurance would be responsible for covering the costs of follow-up tests. In essence, therefore, other people are paying for these scans through their insurance premiums.

With more than 90% of study subjects receiving false-positive test results, the psychological effects of CT screens should also be considered. Positive test results take a significant emotional toll on patient and family—an unnecessary toll when no disease actually exists. In addition, patients undergoing multiple follow-up scans for false-positive results could be subject to harmful amounts of radiation. The screening test, then, could cause more harm than good.