Hba1c
Hemoglobin is the molecule that binds oxygen in erythrocytes and distributes it to all cells that need oxygen. Although there are dozens of different types of hemoglobin in normal adults, the majority of hemoglobin in erythrocytes consists of hemoglobin A (97%), about 2.5% HbA2, and about 0.5% HbF. Apart from these, dozens of different types of hemoglobin can be encountered. There are also sub-modifications of the hemoglobin A molecule. For example, HbA1a, A1b and A1c are detectable modifications. In other words, HbA1 consists of the sum of HbA1a, HbA1b and HbA1c. In fact, two separate Hb components of HbA1a were detected. These are HbA1a1 and HbA1a2.
The durable structure formed by the binding of HbA1 with glucose has been defined as HbA1c by the International Society for Clinical Biochemistry (IFCC). HbA1c is the main glycosylated hemoglobin in the blood and makes up about 80% of HbA1.
HbA1c is the most abundant minor hemoglobin in normal human erythrocytes. It constitutes 5% of total hemoglobin. However, it increased 2-3 times in patients with diabetes. The average normal level of HbA1c is 4-6%.
Because the erythrocyte membrane is freely permeable to glucose, HbA1c is a clinically useful index of mean glucose metabolism over the past 120 days (mean erythrocyte survival). HbA1c reflects glycemic control over the past 2-3 months. Although HbA1c is formed during 120 days of erythrocyte life, recent glycemia within 120 days has more of an effect. Especially in the last month, the effect is half.
The best test for monitoring glucose control in diabetic patients is HbA1c. It should be measured in all patients at baseline and during treatment follow-up.
Blood sample for HbA1c can be taken at any time of the day, regardless of fasting or satiety. However, waiting for the sample taken in the heat may affect the result. It is also important which hemoglobin modifications are studied in the laboratory. It is important that only the HA1c level has been studied, rather than all hemoglobin bound with glucose. Because in some laboratories, for economic reasons, measuring all glycosylated hemoglobin instead of just HbA1c may cause false heights. In addition, there are more than 30 glycosylated hemoglobin methods with different measurement principles in routine use. For this reason, it should be kept in mind that laboratory results can not be compared exactly, but roughly, and patient follow-up should be done with the same method as much as possible.
HbA1c is an indicator of average blood glucose over the past 2-3 months. It is sufficient to do it twice a year in well-controlled patients such as type 2 diabetes. In type 1 diabetics, it should be done every 3 months. The best response in treatment change is reflected in the test result 2-3 months later. Frequent testing is useless.
Minimal changes in HbA1c results may be due to measurement differences. The 1% difference in HbA1c level indicates an average blood glucose change of approximately 35 mg/dl.
While interpreting the HbA1c results, it should be checked whether the patient has symptoms and clinical pictures such as hemoglobinopathy, hemolysis, and uremia. Because these conditions can even change the erythrocyte levels.
HbA1c is not used much in diabetes screening. In addition, HbA1c is not used in blood glucose control in some hemoglobinopathies (HbSS, HbCC, HbSC).
The amount of glucose in the blood or urine or ketone tests in the urine provide information about the current status, while HbA1c is a reliable indicator of the average glycemia in the past. Routinely, HbA1c testing should be performed in all diabetic patients initially to determine glycemic control status and subsequently as part of follow-up therapy.
It may be necessary to keep the HbA1c concentration below 7% in patients receiving treatment, and to review the treatment regimen in cases where the course continues above 8%. Diabetes treatment is a condition that needs to be individualized and followed up and treated according to the individual. For example, although rapid decreases in HbA1c levels reduce the risk of diabetic retinopathy, they also increase the risk of severe hypoglycemia.
Some patients may have very low or normal HbA1c levels even though their blood sugar is very high. In these patients, hematological reasons in which erythrocytes in the blood are fragmented should also be kept in mind.