The formation of glycohemoglobin,especially the hemoglobin A1c(Hb_(A1c))fraction,occurs when glucose becomes coupled with the amino acid valine in theβ-chain of Hb;this reaction is dependent on the plasma concentrati...The formation of glycohemoglobin,especially the hemoglobin A1c(Hb_(A1c))fraction,occurs when glucose becomes coupled with the amino acid valine in theβ-chain of Hb;this reaction is dependent on the plasma concentration of glucose.Since the early 1970 s it has been known that diabetics display higher values of Hb_(A1c)because they have elevated blood glucose concentrations.Thus Hb_(A1c)has acquired a very important role in the treatment and diagnosis of diabetes mellitus.After the introduction of the first quantitative measurement of Hb_(A1c),numerous methods for glycohemoglobin have been introduced with different assay principles:From a simple minicolumn technique to the very accurate automated highpressure chromatography and lastly to many automated immunochemical or enzymatic assays.In early days,the results of the quality control reports for Hb_(A1c)varied extensively between laboratories,therefore in United States and Canada working groups(WG)of the Diabetes Controls and Complications Trial(DCCT)were set up to standardize the Hb_(A1c)assays against the DCCT/National Glycohemoglobin Standardization Program reference method based on liquid chromatography.In the 1990 s,the International Federation of Clinical Chemistry and Laboratory Medicine(IFCC)appointed a new WG to plan a reference preparation and method for the Hb_(A1c)measurement.When the reference procedureswere established,in 2004 IFCC recommended that all manufacturers for equipment used in Hb_(A1c)assays should calibrate their methods to their proposals.This led to an improvement in the coefficient of variation(CV%)associated with the assay.In this review,we describe the glycation of Hb,methods,standardization of the Hb_(A1c)assays,analytical problems,problems with the units in which Hb_(A1c)values are expressed,reference values,quality control aspects,target requirements for Hb_(A1c),and the relationship of the plasma glucose values to Hb_(A1c)concentrations.We also note that the acceptance of the mmol/mol system for Hb_(A1c)as recommended by IFCC,i.e.,the new unit and reference ranges,are becoming only slowly accepted outside of Europe where it seems that expressing Hb_(A1c)values either only in per cent units or with parallel reporting of percent and mmol/mol will continue.We believe that these issues should be resolved in the future and that it would avoid confusion if mmol/mol unit for Hb_(A1c)were to gain worldwide acceptance.展开更多
文摘The formation of glycohemoglobin,especially the hemoglobin A1c(Hb_(A1c))fraction,occurs when glucose becomes coupled with the amino acid valine in theβ-chain of Hb;this reaction is dependent on the plasma concentration of glucose.Since the early 1970 s it has been known that diabetics display higher values of Hb_(A1c)because they have elevated blood glucose concentrations.Thus Hb_(A1c)has acquired a very important role in the treatment and diagnosis of diabetes mellitus.After the introduction of the first quantitative measurement of Hb_(A1c),numerous methods for glycohemoglobin have been introduced with different assay principles:From a simple minicolumn technique to the very accurate automated highpressure chromatography and lastly to many automated immunochemical or enzymatic assays.In early days,the results of the quality control reports for Hb_(A1c)varied extensively between laboratories,therefore in United States and Canada working groups(WG)of the Diabetes Controls and Complications Trial(DCCT)were set up to standardize the Hb_(A1c)assays against the DCCT/National Glycohemoglobin Standardization Program reference method based on liquid chromatography.In the 1990 s,the International Federation of Clinical Chemistry and Laboratory Medicine(IFCC)appointed a new WG to plan a reference preparation and method for the Hb_(A1c)measurement.When the reference procedureswere established,in 2004 IFCC recommended that all manufacturers for equipment used in Hb_(A1c)assays should calibrate their methods to their proposals.This led to an improvement in the coefficient of variation(CV%)associated with the assay.In this review,we describe the glycation of Hb,methods,standardization of the Hb_(A1c)assays,analytical problems,problems with the units in which Hb_(A1c)values are expressed,reference values,quality control aspects,target requirements for Hb_(A1c),and the relationship of the plasma glucose values to Hb_(A1c)concentrations.We also note that the acceptance of the mmol/mol system for Hb_(A1c)as recommended by IFCC,i.e.,the new unit and reference ranges,are becoming only slowly accepted outside of Europe where it seems that expressing Hb_(A1c)values either only in per cent units or with parallel reporting of percent and mmol/mol will continue.We believe that these issues should be resolved in the future and that it would avoid confusion if mmol/mol unit for Hb_(A1c)were to gain worldwide acceptance.
