To get a better idea, Pletcher et al conducted a literature review of all EBCT/CAC studies in asymptomatic patients, ultimately limiting the search to four studies that met their inclusion criteria. When CAC scores were arbitrarily divided into groups of 1-100, 101-400, and >400, the authors report that relative risk estimates increased with higher scores; however, the degree of risk varied widely between studies. Pletcher and colleagues hypothesize that heterogeneity between studiesincluding factors such as tomographic slice thickness, proportion of female subjects, blinded/unblinded adjudication, means of measuring other risk factors, etcmay have accounted for the different study findings.

Overall, however, they conclude, "the relative risks associated with increasing CAC score are at least as large as those associated with established CHD risk factors."

They continue, "We believe our meta-analysis has already answered one important, unresolved question: Does the CAC score predict coronary events even when standard CHD risk factors are taken into account? The answer, at least among the populations represented in these studies, is yes."

Ewy, however, takes issue with the use of "standard CHD risk factors" as a comparator. He points out that "modern" risk factors include such indications as elevated C-reactive protein (CRP) and lipoprotein-associated phospholipase A2 (detected by the recently FDA-approved PLAC test), insulin resistance, fibrinogen, and high-density lipoprotein, among others. "Saying that EBCT adds to the now-primitive risk factors of age, sex, hypertension, smoking status, and LDL cholesterol is really not helpful," Ewy writes. "What we need to know is if EBCT gives any added information when a modern risk panel is also assessed."

And how should physicians act on a positive CAC test? According to Ewy, physicians should not order any type of test unless they plan to use the results to alter their treatment strategies. In Ewy's opinion, a patient with established risk factors should have those risk factors targeted by treatment, regardless of whether an EBCT test shows them to be at high or low risk. "The crude but well-documented risk clusters of age, sex, hypertension, smoking status, and LDL cholesterol used in the study by Pletcher et al are inadequate to ensure the accurate identification of individuals at risk of sudden death or the acute coronary syndrome," he concludes.

As his final stroke, Ewy notes that "most of the advertisements for EBCT neglect to point out the radiation exposure of this test." He says that a standard scan of the heart produces radiation exposure equivalent to six x-rays. Since many people also have their lungs and abdomen scanned at the same time, this exposure jumps threefold.

"The search for the Holy Grail, a fail-safe method for detecting clinically significant coronary atherosclerosis disease, must, unfortunately, continue," Ewy says.

Pletcher couldn't agree more. To heartwire, Pletcher commented that "in general" he agrees with Ewy's concerns about EBCT but that he has kept an open mind. "I agree that EBCT is not the Holy Grail. We need to define exactly what new information this gives us and in what scenarios this measurement might be cost effective in terms of helping clinical decision making." He says he has had patients come into his office with their test results in hand, but he has never himself ordered an EBCT test.

Pletcher also acknowledges that EBCT studies should take into account the "modern risk panel," but with many of these, including CRP, the jury is still out on what they add over and above traditional risk factors.

"What we were trying to do in this paper was bring a cooler head to this whole debate," Pletcher explains. "We're not associated with either the people who are trying to make money off this technology, nor with the cardiologists and others who are reacting against the profiteer-types."

In Pletcher's opinion, Ewy appears to fall into the latter category. "And that's a very common reaction, especially among academics, toward this technology, which has been marketed directly to consumers."

For his part, Pletcher says that he thinks the appropriate studies have not yet been done, but that EBCT "may still end up being a useful tool."