Standardization of Hemoglobin
نویسنده
چکیده
To the Editor: Kobold et al. (1) describe candidate reference methods for hemoglobin A1c (HbA1c) that are based on the identification of hexapeptides from the N-terminus of the b-chains by both a mass spectrometry technique and capillary electrophoresis. Although they are to be congratulated on their efforts in this regard, I wonder whether the (IFCC) definition of HbA1c as hemoglobin modified irreversibly by glucose at one or both N-terminal valines of the b-chains might be a source of difficulty when applied to routine methods. For example, if a patient’s specimen contains, as seems probable, a mixture of modified hemoglobin species such that 10% have both N-terminal valines glycated (b2-G2) and 5% have only one valine glycated (b2-G), the candidate reference methods will determine a HbA1c proportion of 12.5% because this represents the proportion of N-terminal valines that are glycated. It appears unlikely that any routine method will duplicate this result other than by chance. Rather, measurement of intact tetrameric hemoglobin will produce a result of either 10% if only b2-G2 is recognized as HbA1c or 15% if both b2-G2 and b2-G are so recognized. Moreover, it seems possible that these considerations underlie the slope of 0.824 that was found when Mono S chromatography was compared with mass spectrometry [Fig. 8 of (1)]. If b2-G is included in the non-A1c fractions on Mono S, mixtures containing an appropriate proportion of this species, e.g., 10% b2-G2 plus 4.2% b2-G, will give results of 10% for chromatography, 12.1% for mass spectrometry, and a ratio of 0.826 for the comparison, close to the observed ratio. In consequence, routine methods for HbA1c can only be expected to agree with the proposed reference methods when the specimens that are analyzed are devoid of b2-G.
منابع مشابه
2010 Consensus Statement on the Worldwide Standardization of the Hemoglobin A1C Measurement
G lycated hemoglobin concentrations (most commonly hemoglobin A1C; HbA1c) reflect time-averaged blood glucose during the previous 2–3 months and are used as the gold standard for longterm follow-up of glycemic control. Standardization with common calibration was first proposed in 1984 (1). It was only after the publication of the Diabetes Control and Complications Trial (DCCT) study in 1993 (2)...
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