Coronary Artery Calcium Score for Long-term Risk Classification in Individuals With Type 2 Diabetes and Metabolic Syndrome From the Multi-Ethnic Study of Atherosclerosis
Authors: Shaista Malik, Yanglu Zhao, Matthew Budoff, Khurram Nasir, Roger S. Blumenthal, Alain G. Bertoni, Nathan D. Wong
Journal: JAMA Cardiology (2017)

<h3>Importance</h3> Although the risk of type 2 diabetes is considered to be equivalent to coronary heart disease (CHD) risk, there is considerable heterogeneity among individuals for CHD and atherosclerotic cardiovascular disease (ASCVD) risk. It is not known whether coronary artery calcium (CAC) assessment at baseline in individuals with established metabolic syndrome (MetS) or diabetes identifies CHD and ASCVD prognostic indicators during a long follow-up period. <h3>Objective</h3> To compare improvement in long-term prognostication of incident CHD and ASCVD using CAC scores among those with diabetes, MetS, or neither condition. <h3>Design, Setting, and Participants</h3> This study included participants from the Multi-Ethnic Study of Atherosclerosis (MESA), a prospective cohort study of 6814 males and females aged 45 to 84 years without known CVD from 4 race/ethnicity groups (white [38.5%], African American [27.5%], Hispanic [22.1%], and Chinese [11.9%]) recruited from 6 US communities from July 2000 through August 2002. Follow-up for each participant extended to the first occurrence of an incident event, other death, loss to follow-up, or the last follow-up call through December 31, 2013. Data analysis was performed from June 1, 2016, to September 12, 2017. Cox proportional hazards regression models were used to estimate hazard ratios (HRs). Area under the receiver operator characteristic curve and net reclassification improvement were used to compare incremental contributions of CAC score when added to the Framingham risk score, ethnicity/race, and socioeconomic status. <h3>Main Outcomes and Measures</h3> CHD events, including myocardial infarction, resuscitated cardiac arrest, or CHD death. <h3>Results</h3> Of 6814 MESA participants, 6751 had complete risk factor and follow-up data and were included in this study (mean [SD] age, 62.2 [10.2] years; 3186 [47.2%] male). A total of 881 (13.0%) had diabetes, 1738 (25.7%) had MetS, and 4132 (61.2%) had neither condition. After 11.1 mean years of follow-up, CHD events occurred in 84 participants with diabetes (135 ASCVD events), 115 with MetS (175 ASCVD events), and 157 with neither (250 ASCVD events). The CAC score was independently associated with incident CHD in multivariable analyses in those with diabetes (HR, 1.30; 95% CI, 1.19-1.43), MetS (HR, 1.30; 95% CI, 1.20-1.41), and neither condition (HR, 1.37; 95% CI, 1.27-1.47). For incident CHD, net reclassification improvement with addition of CAC score was 0.23 (95% CI, 0.10-0.37) in those with diabetes, 0.22 (95% CI, 0.09-0.35) in those with MetS, and 0.25 (95% CI, 0.15-0.35) in those with neither condition. The CAC score was also a prognostic indicator of CHD and ASCVD after controlling for diabetes duration of 10 years or longer at baseline, insulin use, and glycemic control. <h3>Conclusions and Relevance</h3> In a large multiethnic cohort, the addition of CAC score to global risk assessment was associated with significantly improved risk classification in those with MetS and diabetes, even if diabetes duration was longer than a decade, suggesting a role for the CAC score in risk assessment in such patients.