A study published in the January 14 issue of the Journal of the American Medical Association provides evidence that measuring the coronary artery calcium score on EBT scans (also known as the Ultrafast CT scan) can be of real help in some patients.
The EBT scan evaluates the amount of calcium deposited in the coronary arteries. Such calcium deposits usually are seen in the plaques that accompany coronary artery disease; thus, the higher the calcium score, the higher the likelihood that coronary artery disease is present. Unfortunately, the test has been plagued both by "false positive" results (i.e., positive EBT scans in the absence of significant coronary disease) and to a lesser extent, by false negative results (i.e., negative EBT scans in the presence of significant coronary disease.) For this and other reasons, the usefulness of EBT scans has been very controversial among cardiology specialists - some tout this test as a valuable screening tool, while others castigate it as a waste of money. ( For a recent and measured review of the pros and cons of the EBT scan, click here.) In mid-2000, the American College of Cardiology and American Heart Association published a consensus document on EBT scans that did not satisfy either camp (but kept them from coming to blows.) One of the recommendations of that consensus document was for further study to clarify the role (if any) of EBT scans in screening patients for the presence of coronary artery disease.
The study published last week would seem to at least partially address this recommendation. The investigators evaluated both the calcium scores obtained by EBT scans and the assessment of risk based on traditional means ( click here for a review of risk assessment) in over 1000 patients who had been screened, and then followed for an average of 8.5 years. They found that, in patients whose risk of developing significant heart problems (as measured by traditional means) was measured as being between 10% - 20% over 10 years, the addition of a high calcium score accurately predicted an actual risk that was significantly higher. In patients whose traditionally-determined risk was low (less than 10% over 10 years) or high (greatehr than 20% over 10 years) the calcium score did not improve the risk estimate as determined by traditional means alone.
The Bottom Line
This new study adds a substantial new clue on how EBT scans might be used in a clinically meaningful way. High calcium scores appear not to mean much in patients who have low risk (in whom high calcium scores are likely to be "falsely positive,") nor in patients whose risk is already very high (in whom yet another indication of high risk doesn't add much information.) In patients with intermediate risk, however, the EBT calcium score appears to identify a subset whose risk is actually higher than traditional methods would indicate. In these patients, a positive EBT scan might appropriately trigger more aggressived risk factor modification, and possibly invasive testing.
So, if you are considering an EBT scan, first calculate your risk based on traditional risk factors. (Again, look here to see how to do that.) If your risk is very low or very high, the EBT scan does not stand to offer much new information. But if your risk falls into the intermediate zone, having an EBT scan would seem to make good sense.