Background: Previous methods to measure glycohemoglobin (GHb) have been time-consuming or imprecise; we therefore developed a new enzymatic assay for GHb. Methods: Blood cells were first hemolyzed, and hemoglobin was digested with protease to yield fructosyl amino acid. Fructosyl amino acid oxidase acts on the fructosyl amino acid and generates hydrogen peroxide, which reacts with chromogens in the presence of peroxidase. Total hemoglobin was measured spectrometrically in the same reaction tube. The results were reported as the ratio of the concentrations of GHb and hemoglobin.
Results:The measured values were comparable to those determined with a HPLC method and with an immunoassay in blood samples from 2854 patients with diabetes. Regression analysis for the enzymatic assay (y) vs the HPLC method (x) produced the following: r ؍ 0.979; slope, 0.994 [95% confidence interval (CI), 0.986 -1.001]; y-intercept, 0.04% (95% CI, ؊0.09% to 0.01%); n ؍ 2854. For the enzymatic assay (y) vs the immunoassay (x), the regression statistics were as follows: r ؍ 0.982; slope, 1.002 (95% CI, 0.995-1.009); y-intercept, 0% (95% CI, ؊0.05% to 0.05%); n ؍ 2854. Conclusions: The values measured by the new enzymatic assay are sufficiently correlated with those of the conventional HPLC method and immunoassay, but the proposed assay for GHb is rapid and has high precision.
Our study underscores the need for clinical laboratories and physicians to be aware of the limitations of their HbA1c assay methods as well as the importance of visual inspection of ion-exchange chromatograms to detect abnormalities caused by the hemoglobin variants. Samples with clinically silent Hb variants should be analyzed by a second method with a different assay principle, preferably a boronate affinity HPLC or an enzymatic assay.
ARKRAY, Inc developed the world's first automatic glycohemoglobin analyzer based on HPLC (1981). After that, ARKRAY developed enzymatic HbA1c assay "CinQ HbA1c" with the spread and diversification of HbA1c measurement (2007). CinQ HbA1c is the kit of Clinical Chemistry Analyzer, which uses fructosyl peptide oxidase (FPOX) for a measurement reaction. This report mainly indicates the developmental background, measurement principle, and future of the enzymatic method HbA1c reagent.
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