THIS PPPT IS ABT HBA1 ENZYME AND ITS FUNCTION

1. HbA1c-Biochemical role
in diagnosis of
diabetes mellitis

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5. Formation of glycated hemoglobin
• In hyperglycaemic condition, proteins in body undergo glycation, a non-enzymatic
process of addition of a sugar to protein.
• When once attached, glucose is not removed from hemoglobin and remain inside the
erythrocyte for the whole life span of RBC.
• Glucose form schiffon base with the N-terminal amino group of proteins which is
reversible.
• Later, ketamines get
formed.

6. • There are two normal variants in a
person, HbA1c constitutes 85% of
the Hb, HbA2 is 4% and HbF is 1%
only.
• In laboratory, only HbA1c is measured
because most of the hemoglobin molecules
are HbA1 type.
• Out of this 85% molecules are HbA1c
type, where glucose is attached to N-
terminal of valine of beta chain of
hemoglobin.
• Rest are HbA1a1, HbA1a2
and HbA1d.

8. The rate of formation of
HbA1c, is directly proportional
to the blood glucose
concentration.

13. • It is unaffected by recent food intake or recent changes in blood
glucose levels.
• The HbA1c level reveals the mean glucose level over
the previous 10-12 weeks.
• The value of HbA1c is expressed as a fraction of the total Hb.
With the level above 6.5% being recommended for
the diagnosis of diabetes by the AMERICAN
DIABETES ASSOCIATION.

14. • Less than 5.6% is NORMAL with average glucose value of less than 110mg/dl.
• 5.7-6.4% is IMPAIRED GLUCOSE TOLERANCE with average glucose value of
126mg/dl.
• 7% is ADEQUATE CONTROL with average glucose value of
154mg/dl.
• 8% is INADEQUATE CONTROL with average glucose value of
183mg/dl.
• 9% is POOR CONTROL with average glucose value of
212mg/dl.

16. • HbA1c sample is stable while blood glucose level is lowered unless precautions are
taken.
• Test may be done at any
time.
• Fasting sample is not
required.
• Not altered by acute factors while many factors will affect plasma
glucose.
• The risk of retinopathy and renal complications are proportionately increased with
elevated glycated hemoglobin value.
• Reflects long-term glucose control, while plasma glucose estimation will show the
result of a particular point of time.
• Better index of predicting
complications.
• Reduction in 1% of glyco-Hb will decrease long-term complications to an extent of
30%.

17. • Fluctuations of HbA1c are postulated to be responsible for long-term
complications of diabetes like retinopathy and nephropathy.
• Therefore, THE AMERICAN DIABETES ASSOCIATION has recommended
that HbA1c is the THE PREFERRED METHOD FOR THE FIRST DIAGNOSIS OF
DIABETES.
• It is unaffected by the recent food intake or recent changes in blood glucose
levels.

18. How often should we do the HbA1c
test?
• Few years ago, the recommendation was that the estimation should
be done every 3 months in all diabetic patients.
• But, it is better to do the test once in 2 months , so that the effect of
the treatment may be identified easily.
• If the value is less than the last month, it indicates that the treatment
is effective.

20. • In column chromatography methods, HbA1c and HbF moves similarly, so
abnormally high values is seen in thalessemia, even though the patient is non-
diabetic.
• Low HbA1c values are seen in conditions where RBC life span is reduced
(eg.anemia, abnormal RBCs, pregnancy) because time averaged value is less in
such conditions.
• HbA1c values are lowered in sickle cell anemia, even though the patient is
diabetic.

21. • DM Vasudevan, Shreekumari S and Kannan Vaidyanathan, Textbook of Biochemistry for
Medical Students, Jaypee Brothers Medical Publishers (P) Ltd. 10th Edition .
• Harper’s Illustrated Biochemistry, International Edition, Mc Graw Hill, Lange, 32nd edition.
• Lippincott Illustrared Reviews, Biochemistry, South Asian Edition, Denise R. Ferrier,7th Edition.
• Hutchison’s Clinical Methods,an integrated approach to clinical practice, Michael Glynn and
William Drake, International Edition, 23rd Edition.
• Harrison’s Principles Of Internal Medicine, Kasper, Fauchi, Hauser, Longo, Jameson, Lascalzo,
Mc Graw Hill, Lange, Vol.2, 19th Edition.
• Davidson’s Principles and Practice of Medicine, Stuart H. Ralston, International Edition,
23rd Edition.