Blog | Tuesday, March 27, 2012

QD: News Every Day--Coronary artery calcium the new risk marker that matters most

Coronary artery calcium scores offered the most statistically and clinically significant value to Framingham Risk Score predictions among 12 coronary heart disease risk markers, a study found.

Coronary artery calcium (CAC) measurement may be the only newer coronary risk factor to add meaningful information to standard risks, such as smoking and diabetes, noted editors of Annals of Internal Medicine, in which the research appeared on March 20. But measuring coronary artery calcium is expensive and exposes individuals to radiation, so its use for coronary risk assessment requires further evaluation.

To assess whether newer risk markers for coronary heart disease risk prediction and stratification improve Framingham predictions, researchers conducted a prospective, population-based study among 5,933 asymptomatic, community-dwelling participants from The Rotterdam Study in the Netherlands.

The research measured traditional coronary heart disease risk factors used in the Framingham score (age, sex, systolic blood pressure, treatment of hypertension, total and high-density lipoprotein cholesterol levels, smoking, and diabetes) and newer risk factors (N-terminal fragment of prohormone B-type natriuretic peptide levels (NT-proBNP), von Willebrand factor antigen levels, fibrinogen levels, chronic kidney disease (CKD), leukocyte count, C-reactive protein (CRP) levels, homocysteine levels, uric acid levels, coronary artery calcium scores, carotid intima-media thickness (cIMT), peripheral arterial disease and pulse wave velocity).

Adding coronary artery calcium scores to the Framingham score improved the accuracy of risk predictions (c-statistic increase, 0.05; 95% confidence interval [CI], 0.02 to 0.06; net reclassification index, 19.3% overall [39.3% in those at intermediate risk, by Framingham]). Levels of NT-proBNP also improved risk predictions but to a lesser extent (c-statistic increase, 0.02; 95% CI, 0.01 to 0.04; net reclassification index, 7.6% overall [33.0% in those at intermediate risk, by Framingham score]). Improvements in predictions with other newer markers were marginal.

Improvements in coronary heart disease risk prediction with other newer risk markers, including cIMT, ankle-brachial index, and pulse wave velocity, which have been shown to be strong predictors of coronary heart disease in other studies, were modest, the authors reported. NT-proBNP may be more useful for coronary heart disease risk prediction at older ages. Although other biomarkers such as fibrinogen levels, CKD, leukocyte count, CRP levels, and homocysteine levels, were independently associated with the risk for later coronary events, their incremental value beyond traditional risk factors was marginal.

"The better performance of CAC score compared with other vascular measures of atherosclerosis probably reflects the disparity in contribution of various vascular beds in the disease process," the authors wrote. "However, because of variations across studies in the number of risk categories and thresholds and in clinical outcomes of interest, it is difficult to make direct comparisons of our findings with those of other population studies."