How reliable is the determination of HbAc

The biggest problem with HbA1c measurement is the fact that both reference values and a given value of a blood sample may differ significantly among various laboratories. In recent years, principally in the USA but in other countries as well, a serious effort of standardization of the various methods has started, using the method used in the DCCT as a reference. There are, however, technical problems that persist, and it is hoped that development of newer methods of determination will permanently solve them. For these reasons, it should be emphasized that HbA1c determination should not be used for diagnosis of DM.

More than 30 methods for HbA1c determination currently exist, based mainly on two principles. The first principle refers to the reduction of the positive charge of the haemoglobin molecule, brought about by glycosylation. The methods of ion-exchange chromatography - the with most significant representative being High Performance Liquid Chromatography (HPLC) that was used in DCCT and UKPDS - are based on this principle. The second principle refers to the detection of alterations in the structure of haemoglobin, brought about by the presence of glucose. The methods of affinity chromatography and some that use antibody reactions (immunoassays) are based on this principle.

Affinity chromatography methods determine the whole glycosylated haemoglobin and report the result either as total GHb or as corrected equivalent of HbA1c.

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