Clinical Importance Of Glycosylated Hemoglobin (HbA1c) In Diabetes Mellitus Patients

Abstract

The HbA1c test (hemoglobin A1c, glycosylated hemoglobin A1c, glycohemoglobin A1c, or A1c test) is a lab test, which reveals average blood glucose over a period of two to three months. Specifically, it measures the number of glucose molecules attached to hemoglobin, a substance in red blood cells 1. People who do not have diabetes generally have an HbA1c level of less than 6 %. This means that less than 6 % of their hemoglobin molecules have glucose permanently attached 2. Based on the results of studies such as the Diabetes Control and Complications Trial (DCCT), which showed that tight blood glucose control could reduce the risk of diabetic eye, kidney and nerve disease, the American Diabetes Association (ADA) recommends that people with diabetes try to keep their HbA1c level below 7% 3.

Full text

Online Journal Pharmainfo.net 2008 March 21
“Clinical importance of Glycosylated
hemoglobin (HbA1c) in diabetes mellitus
patients”.
P. V. Ingle
The HbA1c test (hemoglobin A1c, glycosylated hemoglobin A1c,
glycohemoglobin A1c, or A1c test) is a lab test, which reveals average
blood glucose over a period of two to three months.
Specifically, it measures the number of glucose molecules attached to hemoglobin, a
substance in red blood cells 1. People who do not have diabetes generally have an HbA1c level
of less than 6 %. This means that less than 6 % of their hemoglobin molecules have glucose
permanently attached 2.
Based on the results of studies such as the Diabetes Control and Complications Trial (DCCT),
which showed that tight blood glucose control could reduce the risk of diabetic eye, kidney and
nerve disease, the American Diabetes Association (ADA) recommends that people with
diabetes try to keep their HbA1c level below 7% 3.
Underlying Principle:
In the normal 120-day life span of the red blood cell glucose molecules join hemoglobin,
forming glycosylated hemoglobin. In individuals with poorly controlled diabetes, increases in
the quantities of this glycosylated hemoglobin are noted. Once a hemoglobin molecule is
glycosylated, it remains that way. A buildup of glycosylated hemoglobin within the red cell
reflects the average level of glucose to which the cell has been exposed during its life cycle.
Measuring glycosylated haemoglobin assesses the effectiveness of therapy by monitoring long-
term serum glucose regulation4.
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The HbA1c level is proportional to average blood glucose concentration over the previous four
weeks to three months (some researches state that the major proportion of its value is related
to a rather short term period of two to four weeks). Hemoglobin is the oxygen-carrying
pigment that gives blood its red color and also the predominant protein in red blood cells.
About 90% of hemoglobin is hemoglobin A. (The "A" stands for adult type.) Although one
chemical component accounts for 92% of hemoglobin A, approximately 8% of hemoglobin A is
made up of minor components that are chemically slightly different. These minor components
include hemoglobin A1c, A1b, A1a1, and A1a2. Hemoglobin A1c (HbA1c) is a minor component
of hemoglobin to which glucose is bound. HbA1c also is referred to as glycosylated or
glucosylated hemoglobin 5.
HbA1c levels depend on the blood glucose concentration. That is, the higher the glucose
concentration in blood, the higher the level of HbA1c; and not influenced by daily fluctuations
in the blood glucose concentration but reflect the average glucose levels over the prior six to
eight weeks. Therefore, HbA1c is a useful indicator of how well the blood glucose level has
been controlled in the recent past and may be used to monitor the effects of diet, exercise and
drug therapy on blood glucose in diabetic patients 6.
Healthy HbA1c levels 7:
However target HbA1c levels may vary from person to person. A general range for HbA1c
levels is:
•Less than or equal to 7% is a very healthy HbA1c level
•Between 7% and 8% is a fair HbA1c level and needs work to improve
•Between 8% and 10% indicates your blood glucose levels are too high
•Above 10% indicates your blood glucose levels are extremely high
Importance 2:
Patient’s daily blood glucose tests provide only a snapshot of glycemic control at the moment
you test. The HbA1c test, on the other hand, gives the big picture by showing how patient
blood glucose control has been over the previous couple of months. HbA1c tests are helpful to
physician because they give an immediate indication of patient blood glucose control. It is
certainly easier than ploughing through the last three month’s.
Over a longer period of time, consecutive HbA1c tests may provide an overall trend in your
diabetes control. If HbA1c is progressively raising each time patient visit the clinic then it may
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suggest that your treatment plan needs modifying; if you have Type 2 diabetes. Finally, HbA1c
tests are often used in setting and achieving treatment goals.
A major study, the UKPDS Study 8 published in 2000, managed to quantify many of the
benefits of reducing a high HbA1c level by just 1%.
•A 16% decrease in risk of heart failure
•A 14% decrease in risk of fatal or nonfatal myocardial infarction (heart attack)
•A 12% decrease in risk of fatal or nonfatal stroke
•A 21% decrease in risk of diabetes-related death
•A 14% decrease in risk of death from all causes
•A 43% decrease in risk of amputation
A 37% decrease in risk of small blood vessel disease (e.g. retinal blood vessel disease causing
vision loss).
Diabetic patients who are on oral antihyperglycemic agents should check their HbA1c once a
month. If it is high, patient should change diet and or doctor should change medication of the
patient. When the HbA1c is normal, everything is deemed right. The postprandial blood glucose
level monitoring was declared a new target for optimizing treatment of diabetes mellitus. But
HbA1c determination is the best method of monitoring of long term glucose control 9.
References:
1. http://www.geocities.com/diabeteschart/hba/test.html
2. http://www.diabetes-insight.info/Iwd/management/clinic/DI-HbA1c.asp
3. Diabetes Control and Complications Trial (DCCT),
http://diabetes.niddk.nih.gov/dm/pubs/control
4. http://en.wikipedia.org/wiki/Hemogliobin_A1c# underlying_principle
5. http://www.faqs/diabetes/faq/part2/section_9.html
6. http://www.answers.com/htale
7. http://www.labtestonline.org
8. United Kingdom Prospective Diabetes Study (UKPDS), URL:http://www.dtu.ox.ac.uk
9. http://www.drmirkin.com/diabetes/8698.html. Europen Heart Journal Supplements
2000;2;D36-D38.
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About Authors:
P. V. Ingle
Lecturer, Department of Clinical Pharmacy, R. C. Patel College of
Pharmacy, Shirpur -425405, Dist: Dhule (M.S.), India.
Email- prabhu4ever2000@rediffmail.com; Phone- +91 9421472242;
Fax – 02563- 251808
V. G. Kuchake
R. C. Patel College of Pharmacy, Shirpur, Dist – Dhule, (MS).
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S. J. Surana
R. C. Patel College of Pharmacy, Shirpur, Dist – Dhule, (MS).
G. S. Talele
Jalgaon Zillha Medicine Dealers Society’s College of Pharmacy,
Mamurabad, (MS).
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