Several major factors that affect glycosylated hemoglobin, are you affected?

Author: Wang Xuejing, Chief Physician of Civil Aviation General Hospital

Reviewer: Zhang Yu, researcher at Chinese Center for Disease Control and Prevention

Glycated hemoglobin (HbA1c) is a product formed by the non-enzymatic reaction of glucose and hemoglobin in red blood cells. It mainly reflects the average blood sugar level in the past 2-3 months. It is one of the important indicators for evaluating the blood sugar control status of diabetic patients, and its evaluation value has been widely recognized. However, the measurement results of HbA1c are affected by many factors. Understanding these influencing factors can help us interpret the test results more accurately.

First, HbA1c levels are directly affected by blood sugar concentrations. When blood sugar concentrations remain high, HbA1c levels rise, and vice versa. This is because glucose in the blood can slowly and irreversibly combine with hemoglobin in red blood cells to form glycated hemoglobin. This process is positively correlated with blood sugar concentrations, so HbA1c can be used as a good indicator to evaluate the effectiveness of blood sugar control.

Secondly, the life cycle of red blood cells has an important impact on HbA1c levels. Under normal circumstances, the average life span of red blood cells is about 120 days, and the red blood cells in circulation are renewed every 2-3 months. If the life span of red blood cells becomes shorter, the time for glucose to bind to hemoglobin will be reduced, which can lead to a falsely low HbA1c level. Therefore, when evaluating HbA1c results, it should be considered whether the patient has a disease that affects the life span of red blood cells, such as dialysis, hemolytic diseases, hypersplenism, etc.

In addition, the type of hemoglobin and its variation may also affect the results of HbA1c measurement. Some variant hemoglobins will affect the detection method and cause the HbA1c level to be falsely low or high. At this time, laboratory personnel need to switch to other methods to detect HbA1c. Some people may have a lower amount of hemoglobin A and a higher content of other types of hemoglobin due to genetic factors. In this case, glucose will combine with other types of hemoglobin to form glycated proteins, and the part combined with A1c is not the main component. At this time, laboratory personnel need to switch to other methods to detect all glycated hemoglobin, and HbA1c cannot be used as an indicator for blood sugar monitoring.

Figure 1 Original copyright image, no permission to reprint

It is worth noting that although HbA1c is widely used in the screening and management of diabetes, in my country, due to the lack of a unified standardized process in the early days, there are large differences in test results between different laboratories. However, with the advancement of technology and the advancement of standardization work, it is currently believed that HbA1c ≥ 6.5% can be used as the diagnostic threshold for diabetes.

In actual clinical applications, doctors will conduct a comprehensive assessment by comprehensively considering the patient's HbA1c, fasting blood sugar, oral glucose tolerance test (OGTT) and other test results, as well as the patient's lifestyle, medication and other factors. For example, for patients with inconsistent indicators such as HbA1c, fasting blood sugar, and glycated albumin, doctors need to eliminate the limitations of the test method itself and pay attention to whether the patient has experienced major changes in life or treatment recently, such as stressful events, medication adjustments, etc. These factors may have a short-term impact on blood sugar levels.

For patients with diabetes, regular monitoring of HbA1c is essential for evaluating the effectiveness of treatment. It is generally recommended to test HbA1c every 3-6 months to adjust the treatment plan in a timely manner. For patients with large fluctuations in blood sugar, in addition to HbA1c, they can also better understand the dynamic changes of blood sugar through daily self-monitoring of blood sugar and achieve refined management.

When conducting a fasting blood sugar test, patients need to pay attention to the following points: It is recommended to fast for more than 8 hours, and avoid strenuous exercise and intake of reducing substances (such as vitamin C).

Figure 2 Original copyright image, no permission to reprint

HbA1c and glycated albumin tests are relatively stable and less affected by other factors. HbA1c, in particular, is an important tool in diabetes management because of its high stability and ability to more accurately reflect long-term blood sugar control. However, for glycated albumin tests, patients should avoid consuming large amounts of protein to avoid affecting the accuracy of the test results.