Cutoff Values for Glycated Albumin, 1,5-Anhydroglucitol, and Fructosamine as Alternative Markers for Hyperglycemia

Background: Glycated albumin (GA), 1,5-anhydroglucitol (1,5-AG), and fructosamine have attracted considerable interest as markers of hyperglycemia. This study aimed to evaluate the optimal cutoff values for GA, 1,5-AG, and fructosamine and to determine their respective diagnostic efficacies in relation to hyperglycemia. Methods: We enrolled 6012 individuals who had undergone fasting blood glucose (FBG) and Hemoglobin A1c (HbA1c) tests along with at least one alternative glycemic marker. Receiver operating characteristic (ROC) curves and the upper or lower limit of the reference range (97.5 or 2.5 percentiles) were used to ascertain the optimal cutoff values. Follow-up data from healthy individuals were used to identify patients who developed diabetes mellitus (DM). Results: The ROC cutoff values for GA, 1,5-AG, and fructosamine were 13.9%, 13.3 μg/mL, and 278 μmol/L, respectively, with corresponding area under the curve (AUC) values of 0.860, 0.879, and 0.834. The upper limits of the reference intervals for GA and fructosamine were 15.1% and 279 μmol/L, respectively, and the lower limit for 1,5-AG was 5.3 μg/mL. Among the GA cutoff values, the ROC cutoff had the highest sensitivity. Analyzing the follow-up data showed that lowering the GA cutoff from 16.0% to 13.9% identified an additional 40 people with DM progression. Conclusions: Lowering the GA cutoff values significantly increased the sensitivity of DM diagnosis and enhanced its potential as a screening marker by identifying more individuals with diabetes progression. Conversely, modifications to the cutoff values for 1,5-AG and fructosamine did not confer any discernible diagnostic or predictive advantages.