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Text sizeWashington, DC - Proponents of electron beam tomography (EBT) have long argued that people with asymptomatic cardiovascular disease may be more motivated to reduce their risk of worsening disease if they can see for themselves the calcified plaques building in their arteries. Now, researchers have provided some of the first randomized, controlled trial evidence showing that people who are privy to the results of their EBT tests are no more likely than people receiving standard risk-factor assessment to modify their risky habits over the following year.
Drs Patrick G O'Malley, Irwin M Feuerstein,and Allen J Taylor report their results in the May 7, 2003 issue of Journal of the American Medical Association.1
"The most important thing to take from this is that in a relatively young, asymptomatic screening sample, there's really no role for incorporating EBT or atherosclerosis imaging in trying to motivate folks to modify risk," O'Malley told heartwire.
The findings strike at the heart of an ongoing debate over the value of "screening" asymptomatic patients, particularly since EBT (also known as electron-beam computer tomography [EBCT]) has been vigorously and directly marketed to the public, despite equivocal information on whether it adds anything over and above that provided by traditional risk factor screening. In an editorial accompanying the O'Malley et al paper, Dr Philip Greenland (Northwestern University, Chicago, IL) emphasizes that the study findings must be considered in light of the "self-referred" nature of EBT testing in most cases.2 "EBT is commonly promoted directly to the general public," he notes, typically for the purpose of improving risk prediction and/or providing additional motivation for patients to improve their risk-factor control.
No difference in projected risk score with EBT
O'Malley and colleagues set out with the hypothesis that showing patients a picture of their coronary anatomy would improve motivation to modify risk factors and reduce risk of developing clinical cardiovascular disease, regardless of whether there was evidence of disease or not. Accordingly, 450 asymptomatic US Army personnel between the ages of 39 and 45 were randomized to one of four groups: EBT results provided in the setting of intensive case management or in the context of usual care, or intensive case management or usual care without additive EBT results. (Intensive case management incorporates the patients' "readiness to change" into the risk-factor management, as well as more regular follow-up by telephone and visits with specialized nurses. "Usual care" entails summarized information being sent to primary care provider, who then takes over management of risk factors.)
Out of 406 participants available for one-year follow-up, O'Malley et al report that there was no difference in mean absolute change in projected Framingham Risk Score (FRS) at one-year follow-up for patients who did or did not see EBT images of their coronary arteries at baseline. By contrast, patients who received intensive case management (with or without seeing EBT results) showed a decline in projected risk at one-year follow-up, compared with patients who received usual care (in whom projected FRS actually increased; a statistically significant difference).
When the authors looked at the subset of 59 subjects whose EBT scans actually showed early evidence of coronary artery disease to see if EBT scan prompted risk-factor modification, they saw a nonsignificant trend toward a smaller increase in risk, compared with patients in whom EBT test information was withheld.
No increased motivation, no adverse effects
Of note, while seeing EBT results did not appear to have a positive result on subjects in terms of risk-factor modification, seeing test results also did not appear to affect subjects adversely. "In our study, we did not find any differences in one-year stress, mental health functional status, anxiety, or depressive status among those who received EBT information, intensive case management, or usual care," they write.
Likewise, subjects who saw their test results and were given a score of 0, representing no evidence of calcification, did not appear to have higher increases in projected risk than those who did not receive EBT information, a "reassuring" finding, the authors observe. In other words, "a score of 0 does not convey false reassurance resulting in adverse behavioral outcomes," they write.
In his editorial, Greenland points out that EBT is only one of several relatively new tests purporting to offer information that could be used "to activate a previously unmotivated person to improve unhealthy behaviors." O'Malley et al's results should "stimulate greater scrutiny" of tests such as CRP levels, carotid ultrasonography for measuring intimal-medial thickness, and brachial artery reactivity studies to assess endothelial dysfunction. So far CRP results, and now EBT results, he observes, have failed "to provide the motivational jolt to the average patient."
Would symptomatic patients be more motivated?
O'Malley et al caution that a low prevalence of modifiable risk factors and coronary calcium in their cohort may have complicated their efforts to show an effect of EBT tests on risk-factor modification. The trial consent process may also have excluded the types of patients who might have been more motivated by seeing their calcium risk scores. Finally, the authors do not exclude the possibility that there are other valid reasons for conducting an EBT exam, other than as a patient motivator.
It is important, they say, not to rule out the possibility that older, higher-risk patients would be more motivated by seeing an EBT result. "It's worth exploring this in an older population with a higher prevalence of calcification," O'Malley told heartwire.
On the basis of existing, evidence, however, O'Malley and colleagues conclude that the "motivational power" of an EBT test is not reason enough to justify the screening. "Until there is evidence that adding coronary imaging with conventional risk assessment adds incremental value in improving risk, primary prevention programs should preferentially focus on the detection and intensive management of modifiable risk factors and not anatomic case finding for motivational effect."
