OBJECTIVES: The coronary artery calcium (CAC) score predicts coronary heart disease (CHD) events, but methods for interpreting the score in combination with conventional CHD risk factors have not been established.
METHODS: We analyzed CAC scores and CHD risk factor measurements from 6757 Black, Chinese, Hispanic and white men and women aged 45-84 years in the Multi-Ethnic Study of Atherosclerosis (MESA). CAC was associated with age, sex, race-ethnicity, and all conventional CHD risk factors.
RESULTS: Multivariable models using these factors predicted the presence of CAC (C-statistic = 0.789) and degree of elevation (16% of variation explained), and can be used to update a “pre-test” CHD risk estimate, such as the 10-year Framingham Risk Score, that is based on an individual’s conventional risk factors. In scenarios where a high CAC score is expected, a moderately elevated CAC score of 50 is reassuring (e.g., reducing risk from 10% to 6% in a healthy older white man); but when a low/zero CAC score is expected, even with identical pre-test CHD risk, the same CAC score of 50 may be alarmingly high (e.g., increasing risk from 10% to 20% in a middle-aged black woman with multiple risk factors). Both the magnitude and direction of the shift in risk varied markedly with pre-test CHD risk and with the pattern of risk factors.
CONCLUSIONS: Knowing what CAC score to expect for an individual patient, based on their conventional risk factors, may help clinicians decide when to order a CAC test and how to interpret the results.