Does the new International Diabetes Federation definition of metabolic syndrome improve prediction of coronary artery disease and carotid intima-media thickening?

BACKGROUND: Metabolic syndrome (MS) is associated with increased incidence of diabetes and atherosclerotic complications. The new definition of the International Diabetes Federation (IDF) increases the population with this entity, compared to the NCEP ATP III definition.

OBJECTIVES: To study the prevalence of coronary artery disease (CAD) and carotid intima-media thickness (IMT) in patients with and without MS, according to the NCEP ATP III and IDF definitions, and the predictive ability of carotid IMT for CAD.

METHODS: We studied 270 consecutive patients admitted for elective coronary angiography due to suspicion of CAD. All patients underwent ultrasound study of the carotid arteries to measure IMT (the highest value between the right and left common carotid arteries was used in the analysis). Coronary stenosis of > or =70% (or 50% for the left main coronary artery) was considered significant.

RESULTS: By the ATP III definition, 14% of the patients had MS, and these patients had a higher prevalence of CAD (87% vs. 63%, p = 0.004), but no significant difference was found for carotid IMT (1.03 +/- 0.36 mm vs. 0.95 +/- 0.35 mm, p=NS). With the IDF definition, 61% of the patients had MS; this group was slightly older and included more women. There were no differences in terms of CAD (68% vs. 63%) or carotid IMT (0.97 +/- 0.34 vs. 0.96 +/- 0.39 mm). On multivariate analysis, the ATP III definition of MS predicts CAD (OR 4.76, 95% CI 1.71-13.25, p = 0.003), but the IDF definition does not (OR 1.29, 95% CI 0.74-2.27, p = 0.37). On ROC curve analysis, an IMT of > or = 0.95 mm predicts CAD (AUC 0.66, p < 0.001), with a sensitivity of 52% and specificity of 75%.

CONCLUSIONS: The new IDF definition increases the population with MS, decreasing the capacity to predict the presence of CAD. In our population, neither the ATP III nor the IDF definition showed differences in terms of carotid IMT. Carotid IMT can predict CAD, but with only modest sensitivity.