Background: Extent of atherosclerosis measured by amount of coronary artery calcium (CAC) in computed\r\ntomography (CT) has been traditionally assessed using thresholded scoring methods, such as the Agatston score\r\n(AS). These thresholded scores have value in clinical prediction, but important information might exist below the\r\nthreshold, which would have important advantages for understanding genetic, environmental, and other risk factors\r\nin atherosclerosis. We developed a semi-automated threshold-free scoring method, the spatially weighted calcium\r\nscore (SWCS) for CAC in the Multi-Ethnic Study of Atherosclerosis (MESA).\r\nMethods: Chest CT scans were obtained from 6814 participants in the Multi-Ethnic Study of Atherosclerosis (MESA).\r\nThe SWCS and the AS were calculated for each of the scans. Cox proportional hazards models and linear regression\r\nmodels were used to evaluate the associations of the scores with CHD events and CHD risk factors. CHD risk factors\r\nwere summarized using a linear predictor.\r\nResults: Among all participants and participants with AS > 0, the SWCS and AS both showed similar strongly\r\nsignificant associations with CHD events (hazard ratios, 1.23 and 1.19 per doubling of SWCS and AS; 95% CI, 1.16 to\r\n1.30 and 1.14 to 1.26) and CHD risk factors (slopes, 0.178 and 0.164; 95% CI, 0.162 to 0.195 and 0.149 to 0.179). Even\r\namong participants with AS = 0, an increase in the SWCS was still significantly associated with established CHD risk\r\nfactors (slope, 0.181; 95% CI, 0.138 to 0.224). The SWCS appeared to be predictive of CHD events even in\r\nparticipants with AS = 0, though those events were rare as expected.\r\nConclusions: The SWCS provides a valid, continuous measure of CAC suitable for quantifying the extent of\r\natherosclerosis without a threshold, which will be useful for examining novel genetic and environmental risk factors\r\nfor atherosclerosis.
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