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CAC Improves Risk Prediction Among Low-Risk Women
Study Questions:
Does coronary artery calcium (CAC) testing improve cardiovascular disease (CVD) risk estimation among women thought to be at low risk?
Methods:
Data from women with a 10-year atherosclerotic CVD (ASCVD) risk <7.5% from five large population-based cohorts were used for the present analysis. The cohorts included three from the United States (Dallas Heart Study, Framingham Heart Study, and Multi-Ethnic Study of Atherosclerosis), one from Germany (Heinz Nixdorf Recall study), and one from the Netherlands (Rotterdam Study). CVD events were assessed from the data of CAC scan (performed between 1998 and 2006) until January 1, 2012; January 1, 2014; or March 6, 2015. The primary outcome of interest was incident ASCVD, which included nonfatal myocardial infarction (MI), coronary heart disease (CHD) death, and stroke.
Results:
A total of 6,739 women with a 10-year ASCVD risk score <7.5% were included. Mean age ranged from 44-63 years. Median follow-up ranged from 7-11.6 years. CAC was present in 36.1% of the women. During the follow-up, 165 events occurred, including 64 nonfatal MIs, 29 CHD deaths, and 72 strokes. Compared with the absence of CAC (CAC = 0), presence of CAC (CAC >0) was associated with an increased risk of ASCVD (incidence rates per 1,000 person-years, 1.41 for CAC absence vs. 4.33 for CAC presence; difference, 2.92 [95% CI, 2.02-3.83]; multivariable-adjusted hazard ratio, 2.04 [95% CI, 1.44-2.90]). The addition of CAC to traditional risk factors improved the C-statistic from 0.73 (95% CI, 0.69-0.77) to 0.77 (95% CI, 0.74-0.81) and provided a continuous net reclassification improvement index of 0.20 (95% CI, 0.09-0.31) for ASCVD prediction.
Conclusions:
The investigators concluded that among women at low ASCVD risk, CAC was present in approximately one-third, and was associated with an increased risk of ASCVD and modest improvement in prognostic accuracy compared with traditional risk factors. Further research is needed to assess the clinical utility and cost-effectiveness of this additional accuracy.
Perspective:
These data provide evidence regarding the use of CAC to improve risk calculation among women categorized as low risk by the 10-year ASCVD risk score.
Keywords: AHA Annual Scientific Sessions, Atherosclerosis, Cardiovascular Diseases, Coronary Artery Disease, Cost-Benefit Analysis, Diagnostic Imaging, Incidence, Myocardial Infarction, Plaque, Atherosclerotic, Prevalence, Primary Prevention, Risk Assessment, Stroke, AHA16
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