Calcium deposits in the walls of arteries are part of the process of accumulating plaque, called atherosclerosis. The amount of calcium in artery walls is proportional to the amount of plaque present and is reported as a "calcium score."
Calcium accumulation is an early sign of coronary artery disease and usually precedes the development of actual blockages. However, whether knowing the calcium score (above and beyond traditional risk factors) improves predicting who is at high risk for heart disease is not clear.
Calcium Score and Heart Disease
In the new study, 5,878 patients between 45 and 84 enrolled in the Multi-Ethnic Study of Artherosclerosis (MESA Trial) were evaluated using CT scans to look for calcium in the walls of their coronary arteries.
The participants did not have known cardiovascular disease at the start of the study. The participants included men and women who identified themselves as white, black, Hispanic, or Chinese. They were followed by telephone interviews every nine to 12 months to gather information about hospital admissions, other heart disease events, and death.
By using the CT-derived calcium score in addition to other risk factors, researchers were able to correctly place 77% of the overall study population into high- or low-risk categories. When calcium scores were not included, only 69% of participants were correctly classified.
CT Scan Not Recommended
The researchers say that coronary calcium scores helped reclassify a notable number of patients into more accurate risk categories. Twenty-three percent of patients who experienced events were reclassified to a higher risk category, and an additional 13% who did not experience an event were reclassified as low risk based on CT results.
The researchers conclude that a calcium score, used in conjunction with known risk factors, is likely to improve the ability of doctors to determine if their patients are at risk for developing heart problems over time.
But CT scanning is still not recommended as a routine screening test, the researchers say. This study did not answer the critical question of whether screening for coronary calcium improves patient outcomes. However, it did set the stage for this next phase of research to take place. And the researchers note that a CT calcium scan entails some minor risks, such as exposure to small amounts of radiation, as well as additional costs.
In an accompanying editorial, John P.A. Ioannidis, MD, of the University of Ioannina School of Medicine in Greece, and Ioanna Tzoulaki, PhD, of the Imperial College of Medicine in London, agree. "[The] findings, no matter how promising, do not suffice to recommend this marker for widespread routine use," they write.