Prognostic value of International Diabetes Federation and Adult Treatment Panel III definitions of metabolic syndrome in Type 2 diabetic patients: What makes the difference?

Abstract

The International Diabetes Federation (IDF) proposed new diagnostic criteria for metabolic syndrome (MS), lowering glucose and waist thresholds, and rendering abdominal adiposity necessary for diagnosis. In Type 2 diabetic patients, IDF-defined MS has a lower prognostic value than Adult Treatment Panel III (ATP-III) criteria; this could depend either on lower thresholds for waist, or on the fact that adiposity was made necessary for diagnosis. Information on 3-yr all-cause mortality of a consecutive series of 882 Caucasian Type 2 diabetic outpatients was obtained by the City of Florence Registry Office. Two different modifications of ATP-III criteria were tested: low waist threshold (LWT), with same threshold as IDF, but with abdominal adiposity not considered a necessary condition; and elevated waist as necessary condition (EWNC), with the older ATP-III threshold. Over the follow-up period, 115 (13.6%) deaths were recorded. A significantly higher mortality rate was observed in patients with LWT-, but not EWNC-defined MS, in comparison with the rest of the sample (14.2% vs 13.3%, p=0.705, and 14.7% vs 8.9%, p=0.050, for EWNC and LWT, respectively). Lowering the waist threshold did not reduce prognostic value in comparison with ATP-III definition of MS; conversely, when elevated waist circumference was considered a necessary condition for diagnosis, the predictive value for mortality decreased, irrespective of thresholds used. In Type 2 diabetic patients, modification of thresholds for waist circumference does not alter the prognostic value of MS. However, if abdominal adiposity is considered a necessary condition for diagnosis, the ability of MS to predict all-cause mortality is markedly reduced.