"Know your numbers" is the popular doctors' mantra to help patients understand risk for heart attack and stroke and traditionally includes measures for blood pressure, cholesterol, body mass index and waist circumference. Now another number is under debate: coronary artery calcium score, or CACS.
New research suggests that the calcium score may be needed to accurately calculate risk -- though many doctors remain skeptical as to whether the test is worth its cost in health care dollars and radiation exposure.
Investigators at Northwestern University say they calculated CACS by using sophisticated imaging to visualize the amount of calcium found in the lining of arteries in the heart. In their study of 6,000 patients, researchers said the CACS score pushed more people into the high risk category than traditional risk factors alone -- specifically high levels of bad cholesterol or high blood pressure.
The test for CACS could mean early detection of more patients at risk of a heart attack, said the researchers, whose study was published in the Journal of the American Medical Association (JAMA).
"Almost one-quarter of the people in the study who had heart attacks were considered intermediate risk based on traditional risk factors alone, but were considered high risk once we included their CACS," said Dr. Tamar Polonsky, the lead author and a post-doctoral fellow in cardiovascular epidemiology.
However, "We don't want everybody to run out and get one of these based on these results," Polonsky told ABCNews.com. She said follow up is needed to see if doctors can actually predict a heart attack based on the test in a controlled study.
Critics say CACS may not be worth the cost -- it is not typically covered by insurance -- or health risks posed by radiation exposure during imaging. The authors said one scan for a CACS had roughly the same amount of radiation as two mammograms.
"At present, I do not feel that it adds incremental value above and beyond using more traditional risk prediction and/or using lower-cost, radiation-free measures such as serum markers," said Dr. Merle Myerson, director of the cardiovascular disease prevention program at St. Luke's Roosevelt Hospital in New York. "More research will be needed before [CACS] can be considered for routine use."
Myerson noted that one potential problem is "false positives" -- people who are incorrectly classified as high-risk by their CACS and may not require the treatment they receive.
"The study comments on this and says that 'overtreatment' may not have such bad consequences, but I disagree. There is always a risk to medication and treatment and the risk-benefit ratio must be considered," she said.
While Myerson said the study findings were "useful," other physicians disagreed.
"I strongly disagree with the conclusions of this manuscript. To reclassify a handful of patients, you would have to expose thousands of patients to unacceptable levels of radiation," said Dr. Steven Nissen, who chairs the cardiology department at the Cleveland Clinic.
"Widespread screening using CT calcium scanning would represent a huge and unacceptable economic burden for the health care system," he said, noting that other blood markers were not compared to the CACS measure.
"Calcium scanning has achieved a cult-like following in spite of its relative limited value and high costs. Perhaps more disturbingly, calcium scanning often leads to other unnecessary testing, including cardiac catheterization, which probably explains its popularity in our 'fee for service' health care environment."
The amount of radiation was an issue of contention for some. "The radiation exposure is a concern," said Dr. Randy Wexler, associate professor of clinical medicine at Ohio State University. "It does not stop at one test. I have yet to have a patient go and obtain CACS without the recommendation always being a repeat sometime down the road. More cost. More radiation."
But some doctors saw greater value in the CACS because it might help a doctor convince a patient that lifestyle changes are necessary.
"Consider a forty-ish man with high cholesterol, stage 1 hypertension, and pre-diabetes whose father had [a heart attack] in his 50's and who refuses to take a statin or exercise," said Dr. John Messmer, an associate professor of family and community medicine at the Penn State College of Medicine.
"A high [CACS] could be useful to show him he already has atherosclerosis and should be working aggressively to lower his risk," he said.