Impact of lowering the cut-point for impaired fasting glucose on the distribution of impaired glucose regulation subcategories in Chinese adult population

Abstract

To evaluate the impact of lowering of cut-point value for impaired fasting glucose (IFG) from 6.1 mmol/L to 5.6 mmol/L. by the Expert Committee on the Diagnosis and Classification of Diabetes Mellitus, US, on the prevalence rates of different impaired glucose regulation (IGR) subcategories in Chinese adults, and to explore the ability of the new cut-point to diagnose IGR. The data of 15 564 persons undergoing standard 75 g oral glucose tolerance test (OGTT) in the National Diabetes Mellitus Survey (1994) in Chinese adults (>or= 25 years) were reanalyzed. The prevalence of isolated impaired fasting glucose (i-IFG), isolated impaired glucose tolerance (i-IGT), and combined IFG and IGT (IFG/IGT) were calculated by the new criteria of 5.6 mmol/L <or= fasting plasma glucose (FPG) < 7.0 mmol/L and old criteria of 6.1 mmol/L <or= FPG < 7.0 mmol/L. The sensitivity and specificity of different FPG to diagnosis of IGR were analyzed with the value of blood sugar 2 hour after OGTT as 7.8 mmol/L <or= PG2 h < 11.1 mmol/L as the gold standard. Receiver operator characteristic curve (ROC) was used to determine the best FPG cut-point value for diagnosing IGR. (1) The prevalence of I-IFG, I-IGT, and IFG/IGT were 8.71%, 12.08% and 5.95% when classified by the old criteria, and 21.25%, 6.89% and 11.13% by the new criteria respectively. (2) ROC analysis showed an optimum FPG cut-point to diagnose IGR of 5.6 mmol/L, which yielded a sensitivity of 61.9% and specificity of 63.9%. The decrease of the lower cut-point value for IFG from 6.1 mmol/L to 5.6 mmol/L is associated with a 1.2 time increase of IFG prevalence among Chinese adults. From the viewpoint of minimizing the discrepancy between IFG and IGT, it may be suitable to lower the IFG cut-point value.