Glycated haemoglobin

What is being analysed?
The glycosylated haemoglobin test is used to assess blood glucose control over the 3-4 months before the sample is taken. Glucose in the blood reacts spontaneously with haemoglobin in a chemical process known as glycosylation; the bond between glucose and haemoglobin is stable, so the haemoglobin remains glycosylated inside the red blood cell, whose lifespan is about 120 days. Since the amount of haemoglobin that becomes glycosylated depends directly on the concentration of glucose in the blood, the amount of glycosylated haemoglobin reflects the average blood glucose over the weeks before the sample is taken

How is it used?
When is it requested?
What does the test result mean?
Is there anything else I should know?

How is it used?
Glycosylated haemoglobin is used mainly to monitor blood glucose control in people with diabetes over the three or four months before the sample is taken. Keeping blood glucose normal is the main goal in diabetes and reduces the complications affecting the kidneys, retina, heart and blood vessels and nerves caused by chronic exposure of the tissues to high blood glucose. This test is very useful for monitoring treatment and choosing the most appropriate dosage.
Glycosylated haemoglobin is very often requested when diabetes is diagnosed, to determine how poorly blood glucose is controlled; it may also be requested several times while the patient is working to bring blood glucose under control, and then to check that control is maintained.

When is it requested?
Depending on how well blood glucose is controlled, the doctor may request glycosylated haemoglobin 2 to 4 times a year. The American Diabetes Association (ADA) recommends testing glycosylated haemoglobin 4 times a year in type 1 or type 2 diabetes treated with insulin, or 2 times a year in type 2 diabetes not treated with insulin. At diagnosis or when blood glucose control is poor, glycosylated haemoglobin may be requested more often.

What does the test result mean?
Glycosylated haemoglobin reflects the patient’s glucose control; the lower the value, the lower the risk of complications.

Is there anything else I should know?
Glycosylated haemoglobin does not reflect temporary, acute changes in blood glucose, but the average blood glucose over a period equal to the average lifespan of that person’s red blood cells (generally 120 days in a healthy person). In some haemoglobin disorders, such as sickle cell anaemia, the percentage of glycosylated haemoglobin may be lower than in a healthy person; in these cases glycosylated haemoglobin is less useful as an indicator of blood glucose control. With haemolysis or heavy bleeding, glycosylated haemoglobin may be underestimated.

1. Can glycosylated haemoglobin be measured at home, as blood glucose can?
2. Are all glycosylated haemoglobin tests the same?

1. Can glycosylated haemoglobin be measured at home, as blood glucose can?
At present no reliable home test for glycosylated haemoglobin is available in Italy.

2. Are all glycosylated haemoglobin tests the same?
Not yet. There is an international effort to standardise the glycosylated haemoglobin test. Many organisations are working together as part of the National Glycohemoglobin Standardization Program and/or the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC).