Interpretation of the Coronary Artery Calcium Score in Combination With Conventional Cardiovascular Risk Factors: The Multi-Ethnic Study of Atherosclerosis (MESA)

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. 

PMID: 23884352

Posted in Computed Tomography, Health Policy and tagged , , , .

One Comment

  1. From the Journal Clinical Summaries:

    The coronary artery calcium score is a strong predictor of coronary heart disease events, but it is not always clear how to interpret the score in the context of a patient’s conventional coronary heart disease risk factors, such as blood pressure, cholesterol, and smoking status. This analysis of the Multi-Ethnic Study of Atherosclerosis (MESA) provides a way for clinicians to use conventional coronary heart disease risk factor information about a patient to understand how high a coronary artery calcium score to expect. When the actual score is higher than expected, a clinician’s estimate of that patient’s coronary heart disease risk (the “pretest” risk; eg, from Framingham equations), should be adjusted upward; if it is lower than expected, the clinician’s estimate should be revised downward. This article describes a method for making this adjustment and provides examples to illustrate the importance of individualized interpretation of the coronary artery calcium score. These methods may be useful for clinicians in deciding when to order a coronary artery calcium score and how to interpret the results.

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