Definition of Norma / Prediabetes Cut-off Point for Fasting Glycaemia on the Basis of Glucose Tolerance Test and HbA1c Interrelationships

Unification of the approach to the diagnosis of prediabetes (PD) is hardly in doubt. The borderline between PD and diabetes is recognized by all, as well as the upper and lower bounds of PD according to the results of glycemia 120 minutes after 75 g glucose loading (GL120). There are still ambiguities regarding glycohemoglobin (HbA1c) and fasting glycemia (FG). For determination of the Norma/PD cut-off point for FG, we analyzed 85 nondiabetic glucose tolerance test results (75.0 glucose; Samples of fasting blood, and 30, 60, 90, 120 minutes after glucose loading) by using correlation and regression analysis. Glycemic values were measured in mg/dl, HbA1c values were measured in %. The fact of identifying the relationship between FG and Gl120 (r=+0.52 [95%CI +0.346, +0.659]; p<0.001), as well as between FG and HbA1c (r=+0.59 [95%CI +0.432, +0.713]; p<0.001) were the basis of this study. As a result of using regression analysis, multiple regression equations were obtained. GL0 =-4.2439 + 0.1927 * GL120 + 15.462 * HbA1c If GL120 is equal to 139 mg/dl (in accordance with all recommendations), and HbA1c is equal to 5.9% (in accordance with the recommendations of NICE, Canadian Diabetes Association, Australian Diabetes Association, et al.), the maximal normal value for FG should be equal to 114 mg/dl. If GL120 is 139 mg/dl and HbA1c is 5.6% (as recommended by the American Diabetes Association), the maximum normal value of FG should be 109 mg/dl. The optimal upper limit of normal carbohydrate metabolism is levels of GL120 equal to 139 mg/dl, HbA1c - equal to 5.6%, and FG - equal to 109 mg/dl. Values above these and below diabetic levels (200 mg/dl, 6.5%, and 126 mg/dl, respectively) can be considered as prediabetes.