Glycosylated Hemoglobin Test

Introduction

Diabetes is the second killer among modern diseases, and its harm to the human body is second only to cancer. Controlling blood sugar is the key to preventing cardiovascular and cerebrovascular diseases caused by diabetes. Glycated hemoglobin (hemoglobin-A1c, HbA1c) is a type of hemoglobin (hemoglobin, Hb) contained in human blood. It is the product of the slow, continuous and irreversible non-enzymatic protein glycation reaction between the amino terminal of valine on the β chain of hemoglobin in red blood cells and glucose. Glycated hemoglobin is also called glycated hemoglobin.

In medicine, the glycated hemoglobin index refers to the proportion of glycated hemoglobin in the total hemoglobin content in human blood. Since the lifespan of red blood cells in human blood is generally about 120 days, the glycated hemoglobin content reflects the average blood sugar level in the past 2 to 3 months. The glycated hemoglobin level of adult non-diabetic patients is 3.9%~6.2%. For the diagnosis of diabetes, evaluating the proportion of glycosylated hemoglobin is more stable and reliable than evaluating blood sugar.

Through the monitoring of glycosylated hemoglobin and long-term strict blood sugar control, the development of diabetic complications such as heart, eye, kidney and nerve diseases can be delayed. Even a slight decrease in the proportion of glycosylated hemoglobin is important.

Principle of glycosylated hemoglobin detection

The principle of glycosylated hemoglobin detection is mainly to use the characteristics of long-term stable correlation between glycosylated hemoglobin in the blood and blood sugar level, and to reflect the patient's average blood sugar level in the past 2-3 months by detecting the content of glycosylated hemoglobin. Glycated hemoglobin is a compound generated by the non-enzymatic glycosylation reaction of hemoglobin and glucose, and its generation rate is proportional to the blood sugar concentration. Therefore, when the blood sugar level increases, the content of glycosylated hemoglobin in the blood will also increase accordingly.

The process of glycosylated hemoglobin generation is a slow and irreversible process. In the blood circulation, hemoglobin undergoes glycosylation reaction with glucose to form glycosylated hemoglobin. This process is a non-enzymatic reaction, which is not regulated by insulin, and is therefore not affected by factors such as diet or exercise. Once glycated hemoglobin is formed, it will stably exist in red blood cells for a lifespan of about 120 days. Therefore, the content of glycated hemoglobin can reflect the patient's average blood sugar level in the past 2-3 months.

The principle of glycated hemoglobin detection is based on the quantitative detection of glycated hemoglobin. The commonly used methods are ion exchange chromatography (HPLC) and immunoturbidimetry. Ion exchange chromatography separates glycated hemoglobin from non-glycated hemoglobin in blood samples and quantitatively analyzes the content of glycated hemoglobin through different adsorbents and eluents. The immunoturbidimetry method uses specific antibodies to bind to glycated hemoglobin to form an immune complex, and then uses turbidimetry to quantitatively detect the content of glycated hemoglobin.

The principle of glycated hemoglobin detection is based on the non-enzymatic catalytic glycosylation reaction of hemoglobin and glucose. The long-term blood sugar control of patients is reflected by detecting the content of glycated hemoglobin. The advantage of this detection method is that it is not affected by external factors such as diet and exercise, and can accurately reflect the average blood sugar level of patients in the past 2-3 months. Therefore, glycated hemoglobin testing is of great significance in clinical diagnosis and plays a vital role in blood sugar control and disease management of diabetic patients.

Application of glycated hemoglobin testing in diabetes management

1. Diagnosis and screening of diabetes

Glycated hemoglobin testing can be used for the diagnosis and screening of diabetes. According to the recommendations of the International Diabetes Federation (IDF), glycated hemoglobin ≥ 6.5% can be used as one of the diagnostic criteria for diabetes. At the same time, for people with high-risk factors such as family history of diabetes, obesity, and hypertension, regular glycated hemoglobin testing can help to detect diabetes early and intervene.

2. Evaluate the blood sugar control status of diabetic patients

Glycated hemoglobin testing can reflect the average blood sugar level of diabetic patients in the past 2-3 months, thereby evaluating the patient's blood sugar control status. For patients with poor blood sugar control, doctors can adjust the treatment plan according to the glycated hemoglobin level, strengthen lifestyle interventions such as diet and exercise, or adjust the dose and type of hypoglycemic drugs.

3. Predict the risk of diabetic complications

Glycated hemoglobin levels are closely related to the occurrence of diabetic complications. Long-term high blood sugar levels can cause damage to blood vessels, nerves and other tissues and organs, leading to various complications. By regularly testing the level of glycosylated hemoglobin, doctors can predict the patient's risk of future complications and take corresponding preventive measures.

4. Guiding treatment decisions

Glycated hemoglobin testing plays an important role in diabetes treatment decisions. Doctors can choose appropriate hypoglycemic drugs and develop personalized treatment plans based on the patient's glycosylated hemoglobin level. At the same time, by monitoring the changes in glycosylated hemoglobin levels, doctors can evaluate the treatment effect and adjust the treatment plan in time.

Precautions for glycosylated hemoglobin testing

1. Preparation before testing

Before the glycosylated hemoglobin test, patients should maintain normal eating and rest habits, and avoid factors such as strenuous exercise and mood swings that affect the test results. At the same time, patients should inform their doctors of their medication history, allergy history and other information so that doctors can evaluate the accuracy of the test results.

2. Interpretation of test results

The results of glycosylated hemoglobin testing should be interpreted in combination with the patient's specific situation. The glycosylated hemoglobin levels of different patients may vary and are affected by many factors such as age, gender, and race. Therefore, when interpreting the test results, doctors should comprehensively consider the patient's clinical manifestations, other laboratory test results and other factors for comprehensive analysis.

3. Limitations of the test

Although the glycosylated hemoglobin test plays an important role in diabetes management, it also has certain limitations. For example, in some special cases such as anemia and hemoglobinopathy, the glycosylated hemoglobin level may increase or decrease abnormally, thus affecting the accuracy of the test results. Therefore, when conducting glycosylated hemoglobin testing, a comprehensive analysis should be conducted in combination with the patient's specific situation, and other related tests should be conducted if necessary to eliminate interference factors.

What should the glycosylated hemoglobin of diabetic patients be controlled below?

Different types of diabetic patients have different glycosylated hemoglobin control targets.

*For most non-pregnant adult type 2 diabetic patients, glycosylated hemoglobin is controlled at < 7.0%.

*For type 2 diabetic patients with a short course of disease, young age, no complications, and no cardiovascular disease, blood sugar can be controlled at a level close to normal, and glycosylated hemoglobin can be controlled at < 6.5%, but the premise is that hypoglycemia will not occur as a result.

*For patients with a history of severe hypoglycemia, the elderly, significant complications of diabetes, or other serious diseases, or a long course of diabetes, who still find it difficult to achieve conventional treatment goals despite diabetes self-management education, appropriate blood sugar monitoring, and effective doses of multiple hypoglycemic drugs including insulin therapy, the glycated hemoglobin control target can be relaxed to < 8.0%.

*For patients with type 1 diabetes, glycated hemoglobin should be controlled at < 7.5% in childhood and adolescence, and < 7.0% in adulthood. Avoiding hypoglycemia is also an important prerequisite.

*For pregnant women diagnosed with gestational diabetes during pregnancy, glycated hemoglobin during pregnancy should be controlled below 5.5%.

*For pregnant women who have been diagnosed with diabetes before pregnancy, glycated hemoglobin during pregnancy should be controlled below 6.0%.