Comparison of analytical performance of three different methods for determination of glycated hemoglobin

Background: The utility of HbA1c for long term assessment of glycemic control requires an accurate, precise and robust measurement system. Currently, immunoassay and HPLC are the most popular methods for HbA1c estimation. Merck Life Sciences has introduced a fully automated direct enzymatic method for quantification of HbA1c from whole blood on MINDRAY chemistry system. Methods and Findings: HbA1c level of 178 randomly chosen subjects was quantified using three Methods as follows: Cation-exchange High Performance Liquid Chromatography (HPLC) [Shimadzu LC-20 AT], Chemiluminescence Microparticle Immunoassay (CMIA) [Abbott architect i2000SR] and enzymatic assay [Mindray BS 400]. HPLC was accepted as comparative method. The analytical performances of the methods were evaluated with imprecision, bias estimation and comparison studies. There was good concordance between the results from CMIA and enzymatic assay when compared with HPLC (r=0.97 and r=0.96, respectively). The Bland Altman plots showed a favorable agreement between the methods, 95% of values were lying within ± 2 SD range from the mean. The average HbA1c measured by HPLC (6.8%) was higher than both the other methods (CMIA 6.4%, enzymatic assay 6.6%). Conclusion: All methods proved to be sufficiently reliable and the results of these methods showed a strong correlation; though the Direct Enzymatic HbA1c Assay in addition to having all the advantages of both the HPLC and immunoassay methods in areas of accuracy, precision, and applicability to chemistry analyzers, is cost effective, simpler and has less interferences plus it does not require a separate measurement of total hemoglobin content in samples.