Incremental value of ABI and CAC beyond traditional risk markers in long-term prediction of cardiovascular disease incidence in participants with diabetes and impaired fasting glucose: Multi-Ethnic Study of Atherosclerosis.

Background And Aims: Subclinical atherosclerosis (SA) diagnosis is key to primary prevention of atherosclerotic cardiovascular disease (ASCVD). SA is common among diabetics. Ankle brachial index (ABI) and coronary artery calcium (CAC) are markers of SA. This study examined whether adding ABI and CAC to diabetic individuals improved ASCVD risk prediction beyond established risk factors.

Methods: MESA is an observational cohort of 6814 participants without clinical cardiovascular disease. All participants with diabetes and impaired fasting glucose were included in the analysis. The association between CAC, ABI, and incident ASCVD, and all-cause mortality was examined using Cox proportional hazard regression. The risk prediction models including ABI and/or CAC in addition to standard risk factors alone were compared.

Results: Of the 1719 participants, 55% were male and average age was 64 (±9.6) years old. Participants with diabetes or impaired fasting glucose with higher CAC and lower ABI had higher ASCVD and all-cause mortality. ABI and CAC enhanced ASCVD discrimination over standard risk factors, with C-index (95% CI) of 0.689 (0.66, 0.718) for risk factors alone, 0.696 (0.668, 0.724) for ABI, 0.719 (0.691, 0.747) for CAC, and 0.721 (0.693, 0.749) for CAC + ABI. Similarly, for all-cause mortality, both CAC and ABI improved risk discrimination in addition to standard risk factors alone.

Conclusions: In a large population-based study of individuals with diabetes or impaired fasting glucose, the addition of ABI and CAC to conventional risk factors improved 10-year ASCVD risk prediction. ABI and CAC are non-invasive and cost-effective tests; therefore, these markers should be included into ASCVD risk stratification for primary prevention in the diabetic and impaired fasting glucose population.