Evaluating CMR

The Insulin Resistance Atherosclerosis Study

One of the few prospective population studies to compare NCEP-ATP III, IDF, WHO, and hypertriglyceridemic waist criteria is the Insulin Resistance Atherosclerosis Study (IRAS) (1). This study followed 822 subjects 40 to 69 years of age without diabetes for 5.2 years. A total of 148 individuals developed type 2 diabetes over the follow-up period. The best predictor of incident diabetes was impaired glucose tolerance. The prevalence of the metabolic syndrome was 27.5%, 34.4%, 39.5%, and 18.4% with NCEP-ATP III, WHO, IDF, and hypertriglyceridemic waist criteria, respectively. This study is valuable in that it used many statistical models to evaluate the association between metabolic syndrome criteria and incidence of diabetes. NCEP-ATP III criteria showed the strongest association with incident diabetes with an odds ratio (OR) of 4.14 (95% CI, 2.79-6.16). The ORs were 3.68 (95% CI, 2.48-5.45), 3.40 (95% CI, 2.28-5.06), and 2.51 (95% CI, 1.68-3.75) for WHO, IDF, and hypertriglyceridemic waist clinical criteria, respectively. The area under the receiver operating characteristics curve (AROC), which plots the true-positive rate vs. the false positive rate graphically, was also higher with NCEP-ATP III criteria (0.69). The AROC was 0.68 for both WHO and IDF criteria and 0.64 for hypertriglyceridemic waist. The population attributable risk (PAR), which is an estimate of the proportion of CVD in a population attributable to the metabolic syndrome, was very similar between NCEP-ATP III, WHO, and IDF (46.3%, 48.0%, and 48.7%, respectively) criteria and lower with hypertriglyceridemic waist criteria (21.7%). The authors of the IRAS study concluded that IDF and NCEP-ATP III criteria predicted diabetes at least as well as WHO criteria, suggesting that measuring insulin sensitivity with clamp techniques and measuring microalbuminuria are not necessary to predict diabetes from a clinical diagnosis of the metabolic syndrome.