European journal of molecular biology and biochemistry

GLYCATED HAEMOGLOBIN: THE YESTERDAY, TODAY, AND TOMORROW!

Matin Ahmad Khan*, Nirmal Kumar Gadiya, Navin Kumar Sinha, Mahendra Prasad

mak5962@hotmail.com

T1DM Type 1 Diabetes Mellitus ,T2DM Type 2 Diabetes Mellitus, ADA American Diabetes Association DCCT Diabetes Control and Complication Trial, UKPDS United Kingdom Prospective Diabetes Study, OGTT Oral Glucose Tolerance Test, PCPG Post Challenge Plasma Glu

Glycated haemoglobin has been in use to monitor control of blood glucose in diabetic patients for about three decade as the 'gold standard' for monitoring glycaemic control , as a predictor of diabetic complications and as a screening tool for diagnosis of DM and metabolic syndrome . It provides an average blood glucose level during preceding 10 - 12 weeks. It is a very convenient blood test, can be done in any clinical setting regardless of prandial state. There were thirty different laboratory methods available to measure glycated haemoglobin with significant variability of results on same sample. IFCC developed a new reference method to measure the glycated haemoglobin, and the method is accepted worldwide as only valid anchor for the measurement of HbA1c. In 2009 International expert committee recommended the use of HbA1c to diagnose diabetes with a threshold 6.5%. IFCC recommended the use of a new unit, i.e. mmol HbA1c/mol of total haemoglobin in place of percentage. Meanwhile a trial was conducted to find out relationship between average blood glucose and glycated haemoglobin, and a linear regression equation was developed to measure average blood glucose from HbA1c. Using the equation one can calculate average blood glucose from glycated haemoglobin in mmol/mol. This average blood glucose will be reported as "eAG" (estimated average glucose) and it will be used to monitor glucose control as eGFR (estimated glomerular filtration rate) is used to monitor renal function in chronic kidney disease patients. How easy or difficult would it be to abandon a term and a unit, in use for three decades and introducing a new unit (mmol/mol) and even a new term (eAG); only time will tell. Health professionals will need to familiarize with new term and units, they will also have to spend more time with their patients to educate them about new developments. This review provides an update on the optimal HbA1c targets, its reliability in control of diabetic complications, limitations of test results and its importance in control of diabetes patients and their complications, various cut-off values obtained in studies performed both in India and worldwide. Diagnostic methods and laboratories are insufficiently standardized for HbA1c in India. The clinician must consider the overall patient profile in addition to a number of local variations and disorders especially hemoglobinopathies /anemias before accepting an abnormal HbA1c value. Supportive or repeat tests may be required leading to increase in cost and delay in diagnosis. In the present Indian scenario, especially the fragmented unorganized health care sector in suburban areas, HbA1c cannot be accepted as a sole and independent test to diagnose diabetes mellitus.