Analytical Performances of an Enzymatic Assay for the Measurement of Glycated Albumin

Background: Short to intermediate integrated glycemic control is best determined by glycated albumin (GA). This assay is appropriate when interpretation of glycated hemoglobin (HbA(1c)) is critical because of hemoglobinopathies, severe anemias, or other factors that affect red blood lifespan as hemodialysis. We evaluated a new assay based on the enzymatic quantification of GA by ketoamine oxidase and an albumin-specific protease. Methods: Limits of blank, detection, and quantification; precision; linearity; accuracy; interferences; correlation with HbA(1c); and serum vs plasma study have been evaluated on ILab (R) systems. Results: Limit of blank, detection, and quantification for GA (g/L) were, respectively, 0.26, 0.36, and 1.15. Repeatability and within-device precision CVs were lower than 2.11%, 1.61%, and 1.56% for GA (g/L), albumin (g/L), and GA%, respectively. Linearity for GA (g/L) and GA% was 1.2-36.8 and 5.5-92.2, respectively. Highest deviation from linearity was<11% and recovery was higher than 90%. Accuracy against the certified ReCCS Japan Clinical Chemistry Reference Material (JCCRM) 611 was <1%. Classical interfering substances had no significant impact. Correlation of GA% between ILab (R) Taurus and ADVIA system was y = 1.02[GA%]+0.25; R-2 = 0.994. No difference was found in the determination of GA% in serum vs plasma. Conclusions: GA enzymatic assay is a reliable, fully automated method allowing accurate and precise determination of GA in a routine laboratory.