The metabolic syndrome using the National Cholesterol Education Program and International Diabetes Federation definitions among urbanised black South Africans with established coronary artery disease

Background. The International Diabetes Federation (IDF) introduced a new definition of the metabolic syndrome (MS) that emphasises ethnic-specific cut-offs for waist circumference (WC). Objective. To compare MS prevalence rates using the National Cholesterol Education Program Adult Treatment Panel III (NCEP: ATP III) and IDF definitions. Methods. Anthropometric data, fasting biochemical variables and MS prevalence rates were measured in 40 black patients with established coronary artery disease (CAD). Glucose metabolism was assessed using the oral glucose tolerance test (OGTT), and insulin-mediated glucose disposal (M-value) was evaluated using the hyperinsulinaemic euglycaemic clamp technique. Results. Based on the NCEP: ATP III definition, MS prevalence was 60% and using the IDF definition, it was 57.5%. The two definitions similarly classified similar to 83% of patients as being MS positive or MS negative. Lower WC cut-offs in the IDF definition classified greater numbers of men and women as having WC as a risk factor -IDF v. NCEP: ATP III men 57.6% v. 36.4%; women 100% v. 71.4%. Impaired glucose tolerance (IGT) was found in 12 of the 40 patients (30%) and diabetes mellitus (DM) in 8 (20%). Mean M-value was reduced in IGT and DM groups compared with the normal group, significantly so in the DM group (p = 0.01). Conclusions. NCEP: ATP III and IDF definitions both generated similar MS prevalence estimates. The two definitions similarly identified the presence or absence of the MS in the majority of patients. The IDF definition classified greater numbers of men and women as having WC as a risk factor. There was a high prevalence of previously undiagnosed IGT and DM in our South African black patients with established CAD.