Comparison of ADA and WHO screening methods for diabetes mellitus in obesepatients

Aims To compare the performance of fasting glycaemia (FG) and oral glucose tolerance testing (OGTT) in screening for diabetes mellitus in obese patien ts. Methods A consecutive series of 528 (445 female, 83 male) obese (body mass index > 30 kg/m(2)) outpatients, aged 45.2 +/-: 14.3 years, was studied wit h FG and OGTT. The association of categories of glucose tolerance (diabetes and impaired glucose tolerance (IGT)) and fasting glycaemia (diabetes and impaired fasting glucose (IFG)) with hypertension and hyperlipidaemia were also assessed. Results Prevalence of diabetes and IGT were 20.1 and 22.9%, respectively. F G (> 7 mmol/l) had a sensitivity of 56.7%. Using FG > 6.1 mmol/l, and OGTT in those above the threshold, the sensitivity for diabetes would have been 89.6%, with a positive predictive value of 59.0%, but 68.8% of cases of IGT would not have been detected. Patients with impaired fasting glucose (FG o f 6.1-7.0 mmol/l) showed lower insulin sensitivity and impaired beta cell f unction, and a weaker association to hypertriglyceridaemia, when compared t o IGT. Conclusion FG > 7.0 mmol/l does not show a sufficient sensitivity for the s creening of diabetes in obese patients. FG > 6.1 mmol/l has a satisfactory sensitivity for diabetes, but not for IGT. IFG has different pathophysiolog ical features than IGT and cannot be assumed to have the same prognostic va lue of IGT.