Download Hb A1c by Dr Sarma

Paradigm shift in Diabetic care
Dr.R.V.S.N. Sarma, M.D., M.Sc.,
Dr.Sarma@works
How true ?
Once there was a tiger which boasted
that it can run faster than any one.
One day he chased a rabbit and failed to
catch it.
“All right” said the tiger; “of course I
failed on my boast.
But, remember the rabbit was running
for its life and I, for my dinner.”
Now, decide who is the rabbit and who
is the tiger - among we and our patient !
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Dr.E.P.Joslin
“The greatest burden on doctors will
be not the management of diabetes,
but the associated macro and microvascular complications of it.” ..1926
“The goal of therapy in diabetes
should be to make serious efforts to
keep the blood sugar levels as close
normal as possible.” ….. 1929
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Be serious Doctor
1. I am making India the capital of the
world shortly !
2. Already I have a big… family of 200
millions on the globe.
3. I am happily troubling 12% urban and
8.2% of rural Indians.
4. In my name I am sweet but my
effects are very hot !
5. I am not easily controlled (< 45%)
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Haemoglobin
Structure of Hb
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Different Hbs
1.
2.
3.
4.
Fetal Hemoglobin – Hb F
Adult Hemoglobin – Hb A
Sickle cell disease – Hb S
Hemoglobinopathies – Hb C, Hb E
Glucose in the blood reacts with the
Hemoglobin A to form Glycated Hb.
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Glycated Hb - GHb
Different types of Glycation products
are formed from the HbA0 depending
on the carbohydrate moiety – namely
–
–
–
–
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HbA1a1 - Fr 1,6 diphos –N-term. valine
HbA1a2 - Gl 6 phos –N-terminal valine
HbA1b - Other CHO – N-term. valine
HbA1c - Glucose –N-terminal valine
Normally less than 6% of Hb is HbA1c
(Previously called glycosylated Hb.)
Reference values of HbA1c
1.
2.
3.
4.
Less than 6% - Normal
6 to 7.5% - Good control of DM
7.6 to 9% - Unsatisfactory control
More than 9% - Very poor control
Values depend on the method of estimation
They vary from lab to lab.
Note if all GHb is measured instead of HbA1c
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Factors affecting HbA1c
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Acute hyperglycemia
Severe aneamia
Gestational diabetes
Life span of the RBC
Abnormal Hb like S-Hb, Hb C
Serum opalescence -↑TG
On the method of estimation
Estimation of HbA1c
• There are many methods of estimation
• HPLC (High Performance Liquid
Chromatography) – Gold standard.
• Immuno-turbimetric meth. – HbA1cAb
• Affinity chromatography
• Electrophoretic methods
• Method based on chemical reactions.
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HbA1c is ‘weighted’
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How well it measures ?
Lowering Hb A1c reduces risk of complications
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Advantages of HbA1c
• Index of long-term control over 120
days and not a snap shot like PG
• Can be done at any time of day
• Not influenced by diet, exercise,
emotional disturbances on test day
• Useful index in clinical trials
• Useful if missed drugs / default diet
• Useful in DD of stress hyperglycemia
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Limitations of HbA1c
• Cannot be an emergency room test to
titrate Insulin or OHA dosage
• Cannot register hypoglycemia
• More sensitive to sin than repentance –
if it is elevated it confirms poor control,
if it is boarder line, it cannot assure
good control in the recent past.
• Not sensitive enough for use in GDM
•  Anaemia, Uraemia, Pregnancy
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Correlation of MPG - HbA1c
Mean Plasma Glucose =
(33.3 x HbA1C%) - 86
(Nathan et. al. NEJM, vol. 310, No 6, Feb 9, 1994)
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HbA1C %
Mean BG mg %
5
7
9
11
80.5
147.1
213.7
280.3
Glycosylation of hair
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Hair glycosylation using thiobarbituric acid TBA
Glycosylation of hair is  in diabetes mellitus
Both insulin dependent , non-insulin dependent
Glycosylation of hair is proportionate to HbA1c
Due to the presence of hexosyl lysome in hair
Long hair sample provides a long term record.
May have forensic application & in population
studies.
BMJ, 1996, vol. 288 pp. 669-670
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Blood Glucose Monitoring
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Type
Frequency
Sample
Type 2 DM
Monthly
FPG / PPG
Type 1 DM
Stabilized
4-6 times
initially
Twice a week.
6th hourly
to 4th hourly
3 samples
Pregnancy
Once a week.
FPG / PPG
Peri-operative
4-6 times
a day
6th hourly
to 4th hourly
MAGE
“Blood Glucose 80 min. after
breakfast correlates with MAGE
( Mean Amplitude of Glycaemic
Excursions ) throughout the day”
Molnar et. al.
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SMBG
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On intensive insulin therapy
Diabetes in pregnancy
IDDM who lack warning symptoms
of hypoglycaemia
Insulin - requiring diabetics
Diabetics with unusually high/low
RTMG.
Insulin - resistant diabetics on large
insulin doses
Motivated diabetics for tight control.
New era in monitoring control
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