Detecting type 2 diabetes by a single post-challenge blood sample

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 postprandial hyperglycaemia. Therefore, a study was undertaken to develop a postchallenge, onesample mode of diagnosis. OGTT was performed in 240 highrisk 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 nondisease 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 cutoff values. These were identified as the concentrations demonstrating the highest diagnostic efficiency and were lower than the WHO limits. The 2 h postload plasma concentration led to higher efficiency at a cutoff 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 postglucose challenge appeared to be most efficient for the early detection of DM.