Analytical Performance of Two Enzymatic Methods for Glycated Albumin

BACKGROUND: The measurement of glycemic control among patients with diabetes mellitus is important for predicting the risk of diabetic complications. Glycated hemoglobin (HbA1c) measurements have been used for long-term glycemic control in clinical practice. However, glycated albumin (GA) or glycated serum protein (GSP) is a more reliable indicator of glycemic control in the short term (2 - 4 weeks) and an alternative marker of HbA1c in clinical situations with changing red blood cell (RBC) lifespan. Here, we evaluated an analytical performance of the two enzymatic assays commercially available, Lucica GA-L and Autolab GA, for the determination of GA (%). METHODS: For each assay, the imprecision was evaluated based on CLSI EP05-A2. In total, serum samples of 283 subjects were simultaneously tested using the two enzymatic assays for method comparison according to CLSI EP09-A3. Some subjects collected the laboratory data for HbA1c. RESULTS: The GA (%) value of the Lucica GA-L assay showed highly reproducible results with within-run, between-run, and total coefficient of variations (CVs) below 2.4%. The Autolab GA assay also showed reliable results with within-run, between-run, and total CVs below 3.9%. The Lucica GA-L assay showed a very high correlation with the Autolab GA assay (r = 0.9993). However, at the median decision point (MDP, 14.3%), the estimated bias of the Autolab GA assay was 4.5%, exceeding the allowable bias (2.9%) accounting for the biological variation. For the correlation analysis between HbA1c and GA (%), the two assays demonstrated the same pattern, with no statistical differences between the two independent correlation coefficients. CONCLUSIONS: Both GA assays evaluated in this study showed good precision and excellent correlation, but the comparability at MDP did not meet the acceptance criteria.