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

AIM: 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.
METHODS: 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.
RESULTS: 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.
CONCLUSION: 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.