Coronary risk stratification using a risk factor only-based scheme is a weak discriminator of the overall atherosclerotic plaque burden in individual patients compared to coronary CT angiography (CCTA), according to a study published in the January issue of the American Journal of Roentgenology.
The objective of the study was to determine the degree to which Framingham risk estimates and the National Cholesterol Education Program (NCEP) Adult Treatment Panel III core risk categories correlate with total coronary atherosclerotic plaque burden (calcified and noncalcified) as estimated on coronary CT angiograms.
CCTA was performed in 1,653 patients (1,089 men, 564 women) without a history of coronary heart disease. The most common reasons for the exam were family history, hypercholesterolemia, hypertension, smoking and atypical chest pain. Researchers divided the coronary tree into 16 segments; four different methods were used to quantify the amount of atherosclerotic plaque or the degree of stenosis in each segment, and segment scores were combined to give total scores. Framingham risk estimates and NCEP risk categories were calculated for each patient.
Correlation of plaque scores with the Framingham 10-year risk estimates were modest: Spearman's rho was 0.49-0.55. For all comparisons of NCEP risk categories to plaque score categories, the proportion of raw agreement, p0, was less than 0.50. Cohen's kappa ranged from 0.18 to 0.20, the investigators found.
Overall, 21 percent of the patients would have their perceived need for statins changed by using the coronary CTA plaque estimates in place of the NCEP core risk categories; 26 percent of the patients on statins had no detectable plaque, according to the researchers.
The authors concluded that “patients with little or no plaque might be subjected to lifelong drug therapy, whereas many others with substantial plaque might be undertreated or not treated at all.”