Coronary artery calcium (CAC) testing improves coronary heart disease (CHD) risk classification in younger adults, according to research published in the Journal of the American College of Cardiology.
“In a young, multi-ethnic cohort, the addition of CAC to a model comprised of traditional CHD risk factors significantly improved discrimination and risk classification,” the authors wrote. “Our findings suggest that coronary calcium can refine CHD risk prediction in populations younger than those previously studied and at the lower end of the age group targeted by recent guidelines.”
CAC is measured by computed tomography and is an established predictor of CHD. CAC has a greater impact on clinical metrics of discrimination, like C-statistics, and risk classification. The effects of CAC on CHD risk prediction in the younger population are still undetermined.
In an analysis of the Dallas Heart Study, researchers from the University of Texas Southwestern Medical Center examined the data of 2084 participants with a mean age of 44.4. Researchers recorded fatal and non-fatal cardiovascular events and hospital admissions of participants annually from 2000 to 2010.
The researchers evaluated risk factors including age, race, sex, systolic blood pressure, total and high density lipoprotein cholesterol, smoking status, and hypertension treatments. The 10-year risk categories were defined as <6%, 6% to 20%, and >20%.
Participants aged 50 years or older had a higher rate of traditional risk factors and higher CAC scores. The data showed that a total of 57 CHD events, including 7 CHD deaths, 30 nonfatal myocardial infarctions, 8 coronary artery bypass graft surgeries, and 12 percutaneous coronary revascularizations, occurred over a mean of 9.2 years.
The C-statistic for the traditional risk factor model was 0.86 (95% confidence interval [CI] 0.83-0.91), and the added CAC score improved discrimination with a C-statistic of 0.89 (95% CI 0.86-0.93; P=.003).
Increased CAC scores were associated with higher CHD rates in the overall cohort population. Among participants who had a cardiovascular event, the addition of CAC resulted in an upward reclassification of 21%, and among those without a cardiovascular event, there was a downward reclassification of 0.5%. When the data was restricted to hard CHD events (CHD-related death and myocardial infarcation), the addition of the CAC score resulted in a net correct reclassification of 32.4%.
The authors note that the younger population tends to have lower CAC scores, which can make it more difficult to establish short-term risk. However, the early identification of CHD risk provides opportunity to begin early prevention treatment, which can result in a higher number of life-years saved for the younger population.
- Paixao, ARM, Ayers CR, Sabbagh AE, et al. Coronary Artery Calcium Improves Risk Classification in Younger Populations. J Am Coll Cardiol. Oct 14 2015. doi:10.1016/j.jcmg.2015.06.015.