Generality
Glycosylated or glycated hemoglobin A1c (acronym HbA1c ) is a laboratory parameter that measures a particular type of hemoglobin in the blood.
HbA1c values reflect mean blood glucose concentrations over the past three months . Therefore, glycated hemoglobin lets you know if your blood sugar has exceeded the "guard" levels in people with diabetes or at risk of becoming one.
HbA1c is less effective than normal hemoglobin with regards to oxygen transport. Furthermore, glycation of hemoglobin is a major cause of organ damage in the course of diabetic disease.
The glycated hemoglobin examination is not routinely prescribed, but only in people who suspect diabetes or those with a confirmed diagnosis, who are following a cure for hyperglycemia control.
Hemoglobin (Hb)
Hemoglobin (Hb) is the protein contained in red blood cells that carries oxygen to tissues and is responsible for their red color (due to the iron contained in the molecule).
What's this
The glycated hemoglobin - or glycosylated, if you prefer - allows you to broadly evaluate the average blood sugar level in the last two or three months.
It is therefore a very useful test to evaluate the adequacy of the glycemic control of the diabetic patient, recently re-evaluated also in the diagnosis of the disease.
Glycation is the non-enzymatic biological process whereby sugars can bind covalently to proteins. The most abundant blood sugar, glucose, can therefore irreversibly bind to a specific part of hemoglobin, forming HbA1c or glycated hemoglobin. The higher the blood glucose concertation, the greater the percentage of glycated hemoglobin (HbA1c or A1C).
Why do you measure
Given the irreversibility of the glycation, the glycosylated hemoglobin contained in red blood cells (avid of glucose) circulates in the blood for the entire duration of their life (on average 90/120 days). Within certain limits, this is an absolutely normal process, which does not entail any danger to the patient's health, given that glycated hemoglobin continues to perform its function normally. The problems, rather, are related to the high blood glucose levels that go with it.
All these characteristics make the glycated hemoglobin a much more useful parameter than the common glycaemia in the diagnosis and monitoring of diabetes ; glycosylated hemoglobin is in fact an expression of medium-long blood sugar, not of a single moment; as such, it is not subject to acute changes (such as the diet of the previous day or the stress of the exam) and therefore does not require a preventive fast of at least eight hours. Therefore, before taking blood, the patient remains free to eat and drink according to habits.
However, the most typical application of glycated hemoglobin remains the assessment of glyco-metabolic control in the medium and long term; several studies have indeed shown a close correlation between the degree of glycemic control, assessed on the basis of HbA1c levels, and the risk of development and progression of chronic complications of diabetes .
Glycated hemoglobin is used both as an average blood glucose index and as an assessment of the risk of developing diabetes complications. It can also be used for diagnostic purposes according to criteria being defined.
In the diabetic, the efficacy of a drug or a therapeutic act is evaluated through its influence on the levels of glycated hemoglobin.
When to take the exam?
The dosage of glycated hemoglobin should be done at the time of diagnosis of diabetes and every 3-4 months to verify the degree of metabolic control.
In well-compensated patients, its determination is accepted every 6 months, while in the case of severe decompensation a new check can be justified even after only one month.
Normal values
The "normal" value of glycated hemoglobin in the population is between 4 and 5-6%
| Glycated hemoglobin | Glycemic control in the diabetic |
<6.3% | Great |
between 6.3% and 7.1% | Good |
between 7.1% and 9% | Mediocre |
> 9% | Bad |
Current guidelines indicate that the primary goal of diabetes therapies is to maintain glycated hemoglobin levels at concentrations no higher than 7%, better if below 6.5%.
If these values exceed 8%, the treatment must be readily re-evaluated.
The higher the percentage of glycated hemoglobin, the greater the likelihood of developing diabetes complications and aggravating existing ones; this relationship is valid above all with regard to nephropathy, neuropathy and diabetic retinopathy.
High Glycated Hemoglobin - Causes
Glycated hemoglobin (HbA1c) values above 6.5% are indicative of diabetes.
Red blood cells have an average life of 3-4 months. In this period, hemoglobin, exposed to excessive concentrations of glucose, turns into glycated hemoglobin. For this reason, people with diabetes generally have HbA1c values in red blood cells much higher than normal.
Although the test is particularly reliable, it should be remembered that all pathologies capable of causing changes in terms of increase or destruction of red blood cells (ie the cells responsible for transporting hemoglobin) can determine an alteration of glycated hemoglobin levels.
In particular, the increase of this value can be influenced by conditions such as:
- High triglycerides (hypertriglyceridemia);
- High bilirubin (hyperbilirubinemia);
- Chronic aspirin intake;
- Opiate addiction;
- Iron deficiency anemia;
- Removal of the spleen;
- Kidney failure;
- Chronic alcoholism.
Low Glycated Hemoglobin - Causes
Low values of glycated hemoglobin are associated with a lower probability of developing, over the years, complications of diabetes affecting the heart, blood vessels, retina and kidneys.
The drop in glycated hemoglobin may be due to factors such as chronic and hemolytic anemias, leukemia and recent bleeding.
How to measure it
Glycated hemoglobin is measured by taking a venous blood sample.
The results will be obtained after a few days.
How often should the test be performed?
The HbA1c dosage should be performed regularly in all diabetic patients, to document the degree of glycemic compensation in the initial assessment and to monitor therapy. In the latter case, to determine whether metabolic control has been achieved, a measurement is recommended approximately every 3-4 months, particularly in subjects with diabetes that is consistently poorly compensated. It should be remembered, in fact, that HbA1c reflects the average glycaemia of the last 2-3 months.
In any case, the dosage frequency depends on the individual clinical condition, the type of therapy being performed and the judgment of the attending physician.
Preparation
Fasting or observing special diets is not necessary for the examination. In fact, the average levels that are measured are referred, for the most part, to periods before the blood test, so eating just before does not affect the result at all.
Interpretation of Results
The test result is always in the form of a percentage, which determines the average blood sugar level in the previous quarter . When the glycated hemoglobin level is equal to or greater than 6.5%, we can talk about diabetes .
If the value is between 6 and 6.5% we find ourselves instead in a prediabetic state .
When we get abnormal results, it means that glucose levels, over a period of time that can vary from weeks to months, have not been well adjusted. If HbA1c is greater than 7%, diabetes is evidently not controlled; consequently, there is a high risk of developing complications.
To remember
The higher the percentage of glycated hemoglobin, the more frequent and serious are the episodes of hyperglycemia that occurred in the weeks preceding the test, so the less diabetes control is.
How to intervene
When the glycated hemoglobin value is too high, the doctor will help to research the possible causes and will evaluate if it is necessary to modify the therapeutic program, based on the patient's needs.
Furthermore, it is possible to intervene on other factors that favor the increase of HbA1c values, including:
- Errors in daily nutrition;
- Sedentary life;
- Prolonged stress;
- Infections / Diseases;
- Overweight / Obesity;
- Inadequate drug therapies.
Continue: Part Two »
