Impaired fasting glucose cutoff value of 5.6 mmol/l combined with other cardiovascular risk markers is a better predictor for incident Type 2 diabetes than the 6.1 mmol/l value: Tehran lipid and glucose study.

Objective: To investigate whether cutoff value of 5.6 mmol/l for impaired fasting glucose (IFG) improves the prediction of Type 2 diabetes mellitus (T2DM) in comparison to the 6.1 mmol/l value.

Research Design And Methods: A total of 5794 non-diabetic subjects aged 42+/-13 years were followed for 6.5 years. T2DM was defined based on the WHO 1999 criteria. Cox regression analysis was used to calculate the relative risk (RR) of developing T2DM. Model discrimination was assessed by calculating the area under the receiver operating characteristic curve (AUC).

Results: During the follow-up, there were 351 incident T2DM. The RR (95% CI) of the 6.1 and 5.6 mmol/l cutoffs were comparable in both univariate and multivariate analysis [9.6 (7.5-12.3) vs. 8.4 (6.4-10.0), respectively in univariate and 2.4 (1.8-3.2) vs. 3.3 (2.6-4.2), respectively in multivariate models]. Using the 5.6 mmol/l cutoff value in the multivariate model significantly improved its discrimination in comparison to the 6.1 mmol/l value [AUC (95% CI): 0.78 (0.74-0.83) vs. 0.74 (0.70-0.79), P<0.01]. Models with impaired glucose tolerance and fasting glucose had the highest AUC of 0.81(95% CI: 0.78-0.85).

Conclusions: The 5.6 mmol/l cutoff value of IFG combined with other diabetes risk factors performs significantly better than the 6.1 mmol/l value for prediction of future T2DM.