Lowered criterion for normal fasting plasma glucose:: Impact on the detection of impaired glucose tolerance and metabolic syndrome

Background. Recently, the Expert Committee of the American Diabetes Association proposed to decrease the lower limit for normal fasting plasma glucose (FPG) levels to 5.6 mmol/L. In this regard, the aim of this study was to determine the effect of lowering the criterion for normal FPG on the identification of subjects with impaired glucose tolerance (IGT) and metabolic syndrome (MS). Methods. We carried out a cross-sectional analysis of a population-based study from Durango, Mexico. This study enrolled 844 apparently healthy men and nonpregnant women aged 34 to 64 years. Diagnosis of IGT was based on 2-h post-load plasma glucose concentration >= 7.8 mmol/L and <11.1 mmol/L, and MS by the definition of National Cholesterol Education Program. Results. The diagnosis of IGT and MS was established in 161 (19.1%) and 190 (22.5%) individuals, respectively. Lowering the cut-off point of FPG from 6.1 to 5.6 mmol/L identified more subjects with IGT, 53/161 (32.9%) vs. 132/161 (82.0%) (p <0.0001). It also identified more subjects with MS, from 88/190 (46.3%) vs. 169/190 (88.9%) (p = 0.0001). Lowering of the FPG cut-off point to 5.6 mmol/L improved the positive likelihood ratio for identifying subjects with IGT from 1.91 to 2.55 and the negative likelihood ratio from 0.81 to 0.27. Lowering the FPG cut-off point to 5.6 mmol/L did not significantly change the positive likelihood ratio for identifying MS from 3.65 to 3.18 and improved the negative likelihood ratio from 0.61 to 0.15. Conclusions. Lowering the cut-off point of IFG to 5.6 mmol/L improves the predictive discrimination of IFG for identifying subjects with IGT or MS. (C) 2006 IMSS. Published by Elsevier Inc.