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Hemoglobin A1c and the Estimated Average Glucose



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HbA1c Methods

Slide 13

July 2009

Hemoglobin A1c methods can essentially be divided into two categories: those that measure HbA1c based upon charge and those that quantitate HbA1c by structure.  A common charge based method utilizes cation-exchange high pressure liquid chromatography, where hemoglobin species elute from the cation-exchange column at different times, depending on their charge, with the application of buffers of increasing ionic strength.  Changes or mutations in the hemoglobin molecule that result in any charge differences may or may not alter the normal elution time of those hemoglobin species when using cation-exchange chromatography; in general, charge based methods are considered to be more susceptible to interference from hemoglobin variants.  Structural methods include boronate affinity chromatography, which separates glycated from non-glycated compounds and is least affected by the presence of variants.  Immunoassays are another structural method commonly used in clinical laboratories and employ the use of antibodies which target the b-N-terminal glycated amino acid in the first 4-10 amino acids, depending upon the manufacturer.  Interferences with immunoassays are rare.  The biggest downfall in using a structural method for measuring A1c is the inability to detect the presence of hemoglobin variants and use of this method should be used with caution in populations where the prevalence of hemoglobin variants is high.

HbA1c Methods

 


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