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Glycated Hemoglobin ( HbA1C )
Glycated Hemoglobin ( HbA1C )
HbA1C is formed by the condensation of glucose with the N-terminal
valine of each B-chain of Hb A to form the unstable Schiff base
(Aldimine,pre –HbA1C) , which then undergoes an Amadori rearrangement to
form astable ketoamine ,HbA1C.
Formation of glycated Hb is irreversible and the blood level depends on:
– life span of RBC .
-Blood glucose concentration.
So it is represent values for glucose over the period preceding 6-8
weeks and provides an additional criterion for assessing glucose
control.
Sample:
– Whole blood is used for analysis.
– blood + EDTA
– heparinized blood.
– capillary blood – one drop on special filter paper.
The specimen should be analyzed as soon as possible . In haemolysates
adducts of hemoglobin with glutathione may be formed . Grossly
hyperlipidaemic samples may give erroneous results by all methods except
some immunological methods.
Methods :
There are 3 major HbA1c testing methods currently available to clinical laboratories. They are:
A- Chromatography based HPLC assay.
B- Antibody based immunoassay.
C- Enzyme based enzymatic assay.
-Determination of Hb A1C is used as aretrospective estimate of the
average blood glucose level over aperiod of 8 to 10 weeks. Therefore
HbA1C is along term measure of glucose metabolism .
-HbA1C should routinely monitor every 3 to 4 months.
– In diabetic pregnancy or intensive therapy , most frequent monitoring ( every 4 weeks) is recommended.
– HbA1C ,dose not has arole in the diagnosis of DM in non pregnant adults or in gestational diabetes (GDM).
Normal range :
( 4.4 -6.4 )%.
Glycated Hemoglobin ( HbA1C )
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