Background: Wide differences in risks for cardiovascular disease (CVD) events associated with coronary artery calcium (CAC) have been reported. We evaluated the relationship of the coronary calcium quartile, on the basis of age-sex cut points from a large sample of asymptomatic patients, to CVD events as a possible standardized means for reporting event risks associated with CAC, in comparison with quartiles of absolute CAC scores.
Methods: We applied age/sex-stratified cut points to 928 asymptomatic men and women (mean age 54 years) followed up for an average of 3.3 years, during which 28 CVD events were confirmed. Cox regression was used to evaluate the relation of the 2nd, 3rd, and 4th quartiles (compared with the 1st), with and without age/sex stratification, to the risk of future CVD events.
Results: The number of events (and percent incidence) that occurred in the 1st, 2nd, 3rd, and 4th quartiles of coronary calcium was 4 (0.9%), 2 (2.0%), 9 (4.5%), and 13 (6.4%) events (P =.001) for the age/sex-stratified quartiles and 4 (1.0%), 0 (0%), 7 (3.0%), and 17 (7.3%) for the absolute score quartiles (P =.001). In multivariable analysis adjusted for other risk factors, there was a modest increase in CVD events seen among those in the 3rd quartile (relative risk [RR] 4.3, P =.02), with a greater risk seen among those in the 4th quartile (RR 6.0, P <.01) (compared with the 1st quartile). This did not differ from use of absolute CAC scores, where RR = 2.6 (P =.14) for the 3rd quartile and RR = 6.4 (P <.01) for the 4th quartile.
Conclusions: Our results suggest that age-sex stratification by percentile rank of CAC is as accurate as absolute CAC scores for predicting CVD events in asymptomatic persons. Ongoing longitudinal population-based studies will provide more definitive data.