HbA1C in diabetes

The article was written by MSc Le Thi Na - Doctor of Hematology, Laboratory Department - Vinmec Times City International General Hospital.

HbA1c is one of the very important test indicators for diabetics because it reflects whether their blood glucose status in the past 3 months has been well controlled or not.

Diabetes is a chronic non-communicable disease, which is increasing rapidly worldwide. The cause may be genetic in the family, or lifestyle changes that lead to overweight and obesity (eg, too much stress, sedentary lifestyle, habit of eating too many high-calorie foods, etc.). .)
According to the American Diabetes Association (ADA) in 2015, the diagnosis of diabetes should be based on 1 of the following 4 criteria:
Fasting plasma glucose ≥ 7 mmol/L. Patients must fast (do not drink soft drinks, can drink filtered water, cooled boiled water) for at least 8 hours (usually overnight fasting from 8-14 hours), or: Plasma glucose at the following time 2 hours of oral glucose tolerance test 75g (oral glucose tolerance test: OGTT) ≥ 11.1 mmol/L. HbA1c ≥ 6.5% (48 mmol/mol). This test must be performed in a laboratory standardized to international standards. Plasma glucose at any time ≥ 11.1 mmol/L in patients with classic symptoms of hyperglycemia. In actual conditions in Vietnam, two simple and effective methods recommended by the Ministry of Health to diagnose diabetes are fasting plasma glucose measurement and HbA1c test measured in a laboratory. international standardization.

Glucose is combined with hemoglobin (Hb) continuously and almost irreversibly throughout the life of the red blood cell, the average in a normal person is 120 days. When blood glucose levels rise above normal for long enough, glucose reacts with Hb without enzyme catalysis to form glycosylated hemoglobin.
Red blood cells have 3 types of Hb: HbA1 accounts for 97-99%, HbA2 accounts for 1-3%, HbF <1%. HbA1 includes 3 groups HbA1a, HbA1b and HbA1c, of which HbA1c accounts for 80%. To express glycosylated hemoglobin, the glycosylated portion of HbA1c is quantified, referred to as HbA1c, in units of %.
The HbA1c concentration will be positively correlated with the mean plasma glucose concentration over the previous 3 months. Therefore, by quantifying HbA1c, it is possible to identify the average blood glucose concentration in the previous 2-3 months of the patient, allowing to evaluate the effectiveness of the diabetes treatment process.

Tests can be taken at any time of the day After a normal meal, Chylomicrons will appear in the blood - a form of exogenous triglyceride transport, which circulates in the blood for about 8-10 hours. completely transformed. Chylomicron causes plasma turbidity and is a major cause of interference in blood test results. Therefore, most blood tests in general and blood glucose tests in particular, for an accurate test result, blood should be drawn in the morning after overnight fasting, at least 8 hours before blood collection. .
The HbA1c test reflects the percentage of glucose bound to hemoglobin in the red blood cells about the last 3 months, so eating at this time should not change the results of the HbA1c test. Therefore, the test can be carried out at any time of the day and does not necessarily require fasting, and still ensures accurate results.
Stable concentrations during storage In red blood cells and white blood cells both contain glycolytic enzymes that consume glucose in whole blood, thereby reducing glucose levels over time, the reduction rate can be 5-7% per hours, but can also rapidly reduce up to 40% in 3 hours. Therefore, the delay in conducting blood glucose testing may artificially reduce the patient's glucose levels, misleading the clinician's diagnosis. To limit errors, blood samples should be anticoagulated with sodium fluoride and tested as soon as possible.
The HbA1c test is performed on whole blood, if not performed immediately, the test is still accurate when stored at 2-80C for 1 week.
Unaffected by factors such as stress, exercise... When the body is under stress, the adrenal gland will release into the blood a number of hormones (adrenaline and norepinephrine) to increase blood glucose, glucose is considered "natural" material" provides energy for physical and mental activities against stress. Stress is not limited to anxiety but also to physical harm, illness, or trauma.
For people without diabetes who have unexplained abnormally high blood glucose levels, stress, or strenuous exercise, before the time of blood collection should be considered. Therefore, in order to test blood glucose accurately, patients need to be instructed to relax completely, avoid staying up late, think a lot, rest, and limit vigorous exercise before taking blood for testing.
Reflects blood glucose for a long time before 8-12 weeks In the blood, glucose is naturally bound to hemoglobin, the amount of glucose bound to this protein is directly proportional to the concentration of glucose in the blood. Because red blood cells remain in the blood for 8-12 weeks before being renewed, HbA1c quantification can be used to reflect average blood glucose levels during that time, providing a measure of long-term glycemic control. term.
Used to guide treatment and control of diabetes HbA1c test results are mainly used to monitor blood sugar control in people with diabetes. The goal of people with diabetes is to keep their blood sugar as close to the normal range as possible because this will limit the complications caused by persistently elevated blood sugar levels, such as: damage to the kidneys, eyes, cardiovascular system and nerves.
The HbA1c test gives us a complete picture of the average blood sugar levels over the last 3 months. It helps patients and doctors assess whether blood sugar control is successful.
It is because of those values ​​of HbA1C that now the HbA1c test is one of the tests performed in the Cardiovascular and Diabetes Screening Package at Vinmec, helping to detect and screen for diabetes early and from there. have a timely and effective treatment plan.