In a recently admitted patient, blood glucose monitoring is as follows:
The two indicators improved over the same period are as follows:
Comparing the above two results with the blood glucose test of admission, we can find that the scope of glycosylated hemoglobin control in patients is up to standard, but the results of glycophanin are significantly low, and in the process of monitoring blood glucose at the end of the fingertip, it is found that patients have two hypoglycemia conditions. Other words:
Patients are very likely to have symptoms or phenomena of hypoglycemia in the past 2 to 3 weeks, but the overall range of blood glucose fluctuations makes glycosylated hemoglobin create an illusion: the patient's blood sugar is stable.
The emergence of glycosylated albumin can make up for some deficiencies in glycosylated hemoglobin in blood glucose detection to a certain extent. But the detailed distinction between the two, you know?
Glycosylated hemoglobin (HbA1c)
HbA1c is the product of a non-enzymatic reaction of hemoglobin's amino group with glucose or other sugar molecules. The formation of this product is directly proportional to the blood glucose concentration and the duration of the concentration of glucose, the higher the blood glucose concentration, the longer the duration, the higher the HbA1c content, and the greater the proportion of total hemoglobin.
Red blood cells live for 2 to 3 months, so they reflect the time of blood glucose in the past 2 to 3 months.
HbA1c is currently a recognized standard for assessing long-term glycemic control in patients with diabetes mellitus and an important basis for adjusting hypoglycemic therapy regimens. In the past, the detection of HbA1c was not standardized enough, so it was not recommended for the diagnosis of diabetes. In recent years, the standardization of HbA1c testing in mainland China has gradually increased, and guidelines recommend that HbA1c ≥ 6.5% as a supplementary diagnostic standard for diabetes.
However, diabetes mellitus can only be diagnosed on the basis of intravenous plasma glucose levels in the presence of sickle cell disease, gestation, glucose-6-phosphate dehydrogenase deficiency, AIDS, haemodialysis, recent blood loss or transfusion, and erythropoietin therapy. HbA1c is also not recommended for screening for cystic fibrosis-associated diabetes.
advantage
HbA1c is very stable and has little variability. Standardized test methods are available to ensure the stability of HbA1c and are the gold standard for blood glucose control.
A large body of evidence-based medical evidence suggests that HbA1c is closely associated with the risk of chronic complications of diabetes. In addition, the detection of HbA1c can reflect long-term blood glucose conditions and is not affected by lifestyle changes such as short-term diet and exercise. It is also more convenient to keep samples, without the need for the patient to have an empty stomach, and blood can be collected at any time, regardless of the impact of eating.
Influencing factors
When applying HbA1c, medical staff should make a judgment based on the patient's specific conditions, such as whether chronic renal insufficiency, hemoglobinopathy, anemia, etc. are combined.
Inadequacies
In addition to not accurately reflecting blood glucose levels in the above cases, the HbA1c test results have a "delay effect" on the assessment after adjusting treatment, and do not accurately reflect the risk of hypoglycemia in patients, nor can they reflect the characteristics of blood glucose fluctuations.
Glycoprotein (GA)
Glycosylated serum proteins are the product of a non-enzymatic reaction between glucose and serum proteins (about 70% albumin) in the blood. Because of its similar structure to fructosamines, the GSP assay is also called the fructosamine assay. However, GSP has poor specificity and is gradually being replaced by GA.
Because albumin has a short half-life in the body, about 17 to 19 days, GA levels reflect the average blood glucose level in diabetics in the first 2 to 3 weeks before detection.
1. More sensitive to changes in blood glucose relatively short term
Because albumin has a shorter half-life in the body, and albumin binds to blood glucose faster than hemoglobin, GA is more sensitive to short-term blood glucose changes than HbA1c.
GA is a good indicator to evaluate the short-term glycemic control of patients, especially the efficacy evaluation of the adjustment of the treatment regimen in patients with diabetes, such as short-term hospitalization of diabetic patients, GA has more clinical reference value than HbA1c.
2. Assist in identifying stress hyperglycemia
When acute stress such as trauma, infection and acute cardiovascular and cerebrovascular events occur, non-diabetic individuals can have hyperglycemia at this time, which is difficult to distinguish from diabetes.
The combination of GA and HbA1c is helpful in determining the duration of hyperglycemia and can be used as an adjunctive test for previous diabetes, thereby objectively assessing the timing and severity of abnormal blood glucose levels to guide diagnosis and treatment. There is potential for diabetes alone as a screening indicator, but it still needs to be tested as a screening indicator alone.
3. Monitoring of special populations
GA is recommended for monitoring blood glucose during pregnancy because it reflects short-term glycemic control levels and is not affected by hemoglobin metabolism or iron deficiency anemia. Blood glucose or GA is a better predictive value for neonatal fat mass than weight alone.
4. In some cases, instead of HbA1c
Ga can act as an alternative to HbA1c in the presence of hematologic changes that affect the half-life of red blood cells and/or the structure or chemical properties of hemoglobin.
Anemia affects the synthesis of red blood cells and the longevity of red blood cells, thus affecting HbA1c levels. Hemolytic anemia and bleeding reduce HbA1c levels, while iron deficiency anaemia, thalassemia, and hemoglobinopathies can elevate HbA1c levels.
5. Correlation with complications
There is evidence that GA, as an important glycosylation product, has a good correlation with chronic complications such as diabetic nephropathy, retinopathy and atherosclerosis.
HbA1c is not a reliable indicator of blood glucose monitoring in patients with diabetes mellitus with CKD, as CKD is often accompanied by factors such as anemia, altered erythrocyte lifespan, and erythropoietin therapy, which can affect the accuracy of HbA1c. However, GA is not affected by anemia and associated treatments and is more appropriate for patients on hemodialysis and peritoneal dialysis.
Although GA is a good indicator of short-term glycemic control in patients, GA test results are unreliable when certain disorders (e.g., nephrotic syndrome, cirrhosis, etc.) affect the rate of albumin renewal. In addition, GA does not accurately reflect the characteristics of blood glucose fluctuations.
HbA1c compared and combined with GA
Application of HbA1c and GA in diabetes screening
Traditional indicators: more cumbersome
At present, the gold standard for the diagnosis of diabetes in the clinic is OGTT, which is inexpensive, but the steps of this test method are more cumbersome, and there is a large coefficient of variation, poor repeatability and long detection time per examination, and some patients in the clinic have obvious digestive tract reactions after ingesting a large amount of sugar water, which is more troublesome.
One of the most commonly used indicators for diabetes screening is FPG. The simple detection of FPG levels will cause the screening population with 2hPG levels ≥ 11.1 mmol/L after sugar load to miss the diagnosis. OGTT and the determination of FPG require at least 8 hours of fasting in the person being tested, and clinical diagnosis cannot be made for some people who visit the hospital in the afternoon, or those who have already eaten.
Can I use HbA1c?
Hemoglobin in the body's blood has a long half-life, and the rate of hemoglobin renewal affects HbA1c, so when making a clinical diagnosis of diabetes, it is difficult for some patients with acute onset, such as type 2 or fulminant type 1 diabetes mellitus with a short duration of less than 3 months, to effectively assess the occurrence and severity of the disease by observing HbA1c levels.
Can I use GA?
When the blood glucose change is most obvious, GA can reflect the body's blood glucose level more timely and accurately, especially for newly diagnosed DM patients with large fluctuations in blood glucose levels, and evaluate the efficacy by measuring their levels when receiving clinical treatment.
The determination of GA can observe the change of blood glucose level in the short term in time, and there is a certain "delay effect" when HbA1c evaluates blood glucose level, so there will be inconsistencies between HbA1c and GA level changes in the clinic.
When the person's HbA1c test result showed 6.1% of the ≥ or ga test result indicated ≥ 17.1%, they needed to be instructed to undergo an OGTT test to confirm the diagnosis of diabetes.
【Reference】
[1] Diabetes Branch of Chinese Medical Association . Guidelines for the prevention and treatment of type 2 diabetes in China (2020 edition). Chinese Journal of Diabetes, 2021, 13(4): 315-409.
[2] Diabetes Branch of Chinese Medical Association . Guidelines for the Clinical Application of Blood Glucose Monitoring in China (2021 Edition). Chinese Journal of Diabetes, 2021, 13(10): 936-948.
[3] Gaolei Sun, Wen Shang, Qingchang Ma, Clinical application value of glycosylated albumin in diabetes mellitus and its complications. Chinese Journal of Frontiers in Medicine (Electronic Edition).
Zhang Junwei, Application value analysis of the joint detection of GA and HbA1c in diabetes screening. Chinese Journal of Medical Innovation, 2021, 18(22): 131-134.
[5] Expert Consensus Committee on Glycosylated Hemoglobin Determination, Expert Consensus on Glycosylated Hemoglobin Determination in 2014. Chinese Journal of Diabetes,2014,6(12):853-858
Source: Endocrine time
Edited by: Yeah Reviewer: Xiao Ran
