Incremental Value of ABI and CAC Beyond Traditional Risk Markers in Long-term Prediction of Cardiovascular Disease Incidence in Participants with Diabetes: Multi-Ethnic Study of Atherosclerosis

Abstract

IntroductionPrimary prevention of cardiovascular disease (CVD) emphasizes detection of subclinical atherosclerosis (SA). Diabetes Mellitus is a high-CVD risk condition with higher prevalence of systemic atherosclerosis. Ankle brachial index (ABI) and coronary artery calcium (CAC) are commonly used measures to detect SA. The primary objective of this study was to evaluate the improvement in CVD risk prediction beyond traditional risk factors after adding ABI and CAC within diabetic participants. MethodsMESA is an observational cohort of 6,814 participants free of clinical cardiovascular disease at baseline. Participants were included in this analysis if they had diabetes or impaired fasting glucose. Cox proportional hazard regression was used to assess the association between CAC score and ABI and outcomes (incident CVD and all-cause mortality). We compared the C-index between a model with traditional risk factors alone and models including ABI and/or CAC. Results1,719 participants were included in the analysis. Average age was 64 years, 55% male, 25% White, 13% Chinese, 34% Black, and 27% Hispanic. Higher CAC and lower ABI were associated with higher risk of CVD (Figure 1) and mortality among people with diabetes. Both ABI and CAC improved CVD discrimination over and above standard risk factors (C-index 0.689 for risk factors alone, 0.719 for CAC, 0.696 for ABI, and 0.721 for both). Similarly for mortality, discrimination was improved over risk factors alone (C-index 0.739) for CAC (0.746), ABI (0.747), and both (0.748). ConclusionThese two subclinical atherosclerosis measures may aid in clinical decision making among those with diabetes.