This study shows CAC is actually less useful in DM than in patients without DM.
In the MESA study (PMID 20424251) which excluded patients with DM, CAC had a NRI of 0.25. In this study, the NRI was only 0.13.
Assessing coronary artery calcium was better than relying on traditional risk factors alone for determining cardiovascular risk.
Diabetes is generally considered to be a risk equivalent of coronary heart disease because of the elevated adverse cardiovascular (CV) event rate in people who have diabetes. Investigators retrospectively analyzed data from 1123 participants with type 2 diabetes (mean age, 61) in a previous study of familial diabetes to investigate whether computed tomography (CT) measurement of coronary artery calcium (CAC) can risk-stratify patients with respect to CV-related mortality.
Eight percent of study participants died of CV causes during an average follow-up of 7.4 years. In multivariate analysis using patients with CAC scores of 0 to 9 as a reference, the odds ratios for CV-related mortality were 2.93 for patients with CAC scores of 10 to 99, 3.17 for 100 to 299, 4.41 for 300 to 999, and 11.23 for ≥1000. The net reclassification index (NRI), a measure of whether patients were reclassified appropriately to low-, intermediate-, or high-risk groups, improved significantly when CAC scores were considered.
This report follows closely on the heels of a meta-analysis that showed that coronary artery calcium scores substantially improved risk stratification for adverse cardiovascular events and ability to identify a low-risk cohort among people with diabetes (JW Gen Med 2013 Apr 9). But these reports do not tell us whether performing CAC scores in our diabetic patients and tailoring our therapy to those scores will lead to better outcomes than current strategies that treat diabetes as a risk equivalent for coronary heart disease. Stay tuned.