In the recent American Diabetes Association (ADA)/WHO recommendations, the oral glucose tolerance test (OGTT) was replaced by the measurement of a single fasting glucose concentration with a decision limit for the detection of type 2 diabetes mellitus (DM) reduced. This proposal, however, misses all cases of isolated post-prandial hyperglycaemia. Therefore, a study was undertaken to develop a post-challenge, one-sample mode of diagnosis.
OGTT was performed in 240 high-risk subjects who were suspected to suffer from type 2 DM. Glucose concentrations were determined at 30 min intervals in the capillary blood, venous blood and plasma, and insulin was determined in venous plasma only. The test results were classified in non-disease and disease group according to the decision limits recommended by ADA/WHO. Furthermore, the early insulin response and an insulin sensitivity index were used to determine new cut-off values. These were identified as the concentrations demonstrating the highest diagnostic efficiency and were lower than the WHO limits. The 2 h post-load plasma concentration led to higher efficiency at a cut-off value of 9.0 mmol/l glucose (162 mg/dl) compared to concentrations of samples taken in the fasting state, at an earlier time of the OGTT, or in venous and capillary blood. Under this condition, 72 diabetic patients (35%) were detected in the study group (n = 207), whereas only 36 (17%) were found with one sample in the fasting state and 53 (26%) with two samples using the ADA/WHO criteria. Therefore, a single venous plasma sample taken after 2 h post-glucose challenge appeared to be most efficient for the early detection of DM.
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