DIABETES IN CHILDREN: HAEMOGLOBIN A1C (HBA1C)

HbAIc is the chemical abbreviation for a compound of glucose and hemoglobin in the blood. Hemoglobin is the red pigment inside red blood cells, and some of it has glucose attached, though most of it does not. We measure this substance in blood as a regular check on young people with diabetes.

The test for hemoglobin A1c

The purpose of the test is to help estimate the quality of control of diabetes over the previous 4-6 weeks. This is helpful in deciding if we should be satisfied with the way we are looking after you or your child with diabetes. We believe that trying to obtain good control is an important way to protect health in later life.

The test measures the quantity of hemoglobin in red cells that has glucose attached to it – glycosylated hemoglobin.

How does the glucose become attached to hemoglobin?

Glucose circulates in the blood, and some passes into the cells in the blood where it attaches to various proteins including hemoglobin. Some of this glucose becomes fixed to the hemoglobin and gradually accumulates over a period of several weeks. The amount that accumulates depends on the average levels of blood glucose concentration over that period of time.

In people who do not have diabetes there will only be a small proportion of glucose hemoglobin. For those with diabetes whose control is not good there will be a high proportion. In this way the proportion or quantity of glucose hemoglobin indicates how close glucose levels are to normal values over the period of time.

Why don’t blood tests at home tell you the same thing?

Blood glucose levels can vary a lot during the day and night, and although we usually only test before meals, they can be quite high after meals or during the night.

The blood tests at home tell us only part of the picture. They are very important however in helping with the day to day management of diabetes and in preventing hypos.

The relationship of HbAlc test and blood glucose tests at home

Both HbA1c and home blood tests tell us about how well we are controlling diabetes. Usually someone who can keep blood tests at home within a satisfactory range (most between 4 to 8mmol/l) will also have a satisfactory level of HbA1c. Sometimes however, the blood tests at home don’t match up with the HbA1c level. There are several possible reasons for this. Perhaps the blood tests at home are inaccurate: the test strips may be out of date or improperly stored. The meter may need calibrating. The child may not be putting enough blood on the strip. It is also possible that blood glucose levels done before breakfast and evening meal are not representative of other times. Thus, someone with a satisfactory HbA1c value, may have high blood tests during the day but low blood glucose levels during the night.

Sometimes teenagers get so fed up with doing blood tests and the disapproval from their parents when the tests are high, that they just make up their results and write down normal values of blood glucose on a test record. Even adults do this sometimes!