This study sought to assess the effect of coronary artery calcium (CAC) on coronary heart disease (CHD) risk prediction in a younger population.
Background
CAC measured by computed tomography improves CHD risk classification in older adults, but the effectiveness of CAC in younger populations has not been fully assessed.
Methods
In the DHS (Dallas Heart Study), a multiethnic probability-based population sample, traditional CHD risk factors and CAC were measured in participants without baseline cardiovascular disease or diabetes. Incident CHD—defined as CHD death, myocardial infarction, or coronary revascularization—was assessed over a median follow-up of 9.2 years. Predicted CHD risk was assessed with a Weibull model inclusive of traditional risk factors before and after the addition of CAC as ln(CAC + 1). Participants were divided into 3 10-year risk categories, <6%, 6% to <20%, and ≥20%, and the net reclassification improvement (NRI) was calculated. We also performed a random-effects meta-analysis of NRI from previous studies inclusive of older individuals.
Results
The analysis comprised 2,084 participants; mean age was 44.4 ± 9.0 years. CAC was independently associated with incident CHD (hazard ratio per SD: 1.90, 95% confidence interval [CI] 1.51 to 2.38; p < 0.001). The addition of CAC to the traditional risk factor model resulted in significant improvement in the C-statistic (delta = 0.03; p = 0.003). Among participants with CHD events, the addition of CAC resulted in net correct upward reclassification of 21%, and among those without CHD, a net correct downward reclassification of 0.5% (NRI: 0.216, p = 0.012). Results remained significant when the outcome was restricted to CHD death and myocardial infarction and when individuals with diabetes were included. The NRI observed in this study was similar to the pooled estimate from previous studies (0.200, 95% CI: 0.140 to 0.258) and the addition of our study to the meta-analysis did not result in significant heterogeneity (I2 = 0%).
Conclusions
CAC scoring also improves CHD risk classification in younger adults.
Key Words
calcium score
coronary heart disease
net reclassification
risk prediction
risk stratification
Abbreviations and Acronyms
CAC
coronary artery calcium
CHD
coronary heart disease
CI
confidence interval
HR
hazard ratio
MI
myocardial infarction
NRI
net reclassification improvement
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Research reported in this publication was supported by the National Center for Advancing Translational Sciences of the National Institutes of Health under award Number UL1TR001105. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH. Dr. Berry is a member of the Speakers Bureau for Merck & Co.; and has received consulting fees from Nihon Corporation. Dr. Rohatgi has received grant support from Merck & Co.; and is a member of the Speakers Bureau for Astra Zeneca. Dr. Kumbhani has received honoraria from the American College of Cardiology. Dr. de Lemos has received consulting fees from Amgen and Abbott Diagnostics; and grant support from Abbott Diagnostics. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.
