Impact of coronary artery calcium on cardiovascular risk categorization and lipid-lowering drug eligibility in asymptomatic hypercholesterolemic men.

BACKGROUND: Application of coronary artery calcium (CAC) for stratifying coronary heart disease (CHD) risk may change the proportion of subjects eligible for risk reduction treatment and decrease cost-effectiveness of primary prevention. We therefore aimed to analyze the impact of CAC on CHD risk categorization.
METHODS: We measured CAC with electron beam computed tomography in 500 asymptomatic untreated hypercholesterolemic men and re-calibrated 10-year Framingham CHD risk by adding CAC score information (post CAC test risk) via an algorithm integrating relative risk and expected distribution of CAC in the population tested. Proportions of low (<10%), intermediate (10-20%) and high (>20%) risk categories, and of eligibility for lipid-lowering treatment, were compared between Framingham risk and post CAC test risk.
RESULTS: In the overall population, post CAC test risk calculation changed risk categorization defined by Framingham assessment alone, with 10% more low risk and 10% less intermediate risk (p<0.01). Risk reclassifications were bidirectional since 30% of high and 30% of intermediate Framingham risk were downgraded to intermediate and low risk categories respectively, while 11% of low and 14% of intermediate Framingham risk were upgraded to intermediate and high-risk categories respectively. Post CAC test risk did not change the proportion of Framingham-based lipid-lowering treatment eligibility in the overall population but decreased it by 8% in intermediate Framingham risk subgroup (p<0.05).
CONCLUSIONS: Addition of CAC to risk prediction resulted rather in downgrading than in upgrading risk and did not change treatment eligibility, except in intermediate risk subjects, less frequently eligible for treatment.