The number of U.S. adults on cholesterol-lowering medication could rise by one-quarter to one-half if doctors were to routinely scan adults’ arteries for plaque buildup, a study suggests.

In 2006, a group of prominent cardiologists, dubbed the SHAPE Task Force, drew up recommendations for a new way to assess middle-aged and older adults’ heart attack risk.

Instead of looking only at standard risk factors - like smoking and high blood pressure - doctors, the task force said, should routinely use CT scans to look for calcium deposits in the coronary arteries.

Calcium is a component of the artery-clogging “plaques” that can eventually trigger a heart attack. Studies show that a person’s calcium score, determined via CT scan, is predictive of his or her odds of suffering a heart attack.

The SHAPE group recommended that most men ages 45 to 75 and most women ages 55 to 75 have a CT scan to help predict their heart risks. The results would also help determine whether they need to start on a statin drug to better control their “bad” LDL cholesterol.

Under the guidelines, the only people who would not be screened would be those already at very high risk of heart attack, and those at very low risk - because they lack all the important risk factors, such as high blood pressure, High cholesterol and diabetes.

In the current study, published in the Archives of Internal Medicine, researchers estimated how such widespread CT screening would affect cholesterol drug prescriptions.

Dr. Raphael See and colleagues at the University of Texas Southwestern Medical Center in Dallas used data from a project called the Dallas Heart Study, which included 2,611 adults who had their coronary artery calcium measured by CT.

The researchers found that if SHAPE guidelines were applied, more people would be considered to have risky LDL levels - though in some cases, CT scan results actually “reclassified” people as having a lower heart attack risk than their traditional risk factors indicated.

On balance, the SHAPE guidelines would increase the number of “statin- eligible” people by 27 percent, See’s team found.

However, the study participants ranged in age from 30 to 65. Leaving out men younger than 45 and women younger than 55, the statin-eligible proportion of patients rose by as much as 48 percent. If there had been any participants older than 65, that increase would likely be greater, the researchers say.

However, an important question left unanswered by this study is whether putting all those extra individuals on cholesterol medication will actually prevent heart attacks and deaths, according to an editorial published with the report.

The study “is necessary and important but does not in itself provide sufficient evidence for the adoption of the SHAPE recommendations,” write Dr. Mark J. Pletcher, of the University of California, San Francisco, and Dr. Philip Greenland, of Northwestern University in Chicago.

Nor does the SHAPE task force represent any official or professional organization. Pletcher and Greenland question where the task force’s funding came from, and whether “conflicts of interest might bias the authors’ judgment.”

The SHAPE recommendations provide “food for thought,” the editorialists write. “But as a guideline for clinical use, SHAPE does not shape up.”

SOURCE: Archives of Internal Medicine, May 28, 2008.