Introduction to HbA1c
Hemoglobin (Hb) that has been chemically bonded to sugar is known as glycated hemoglobin (HbA1c). When present in the bloodstream, the majority of monosaccharides, including glucose, galactose, and fructose, spontaneously and non-enzymatically bind with hemoglobin.
Galactose and fructose are more likely than glucose to do so (13% and 21%, respectively), which is why glucose serves as the main metabolic fuel in humans.
When the sugar-hemoglobin link forms, it means there is too much sugar in the blood, which is frequently a sign of high-concentration diabetes (HbA1c >6.4%). Due to its simplicity of detection, A1C is of great interest. Glycation is the process by which sugars bind to hemoglobin, and the reference system is based on HbA1c, which is defined as a component of beta-N-1-deoxy fructose hemoglobin.
HbA1c is primarily evaluated to identify the three-month average blood sugar level, but it can also be used to diagnose diabetes mellitus and monitor a patient’s glycemic control if they already have the disease.
The test is restricted to a three-month average since a red blood cell typically lives for four months. Since different red blood cells have different lifespans, the test is only used with a three-month limit.
A normal amount of glycated hemoglobin is produced by normal glucose levels. The fraction of glycated hemoglobin rises predictably as the average plasma glucose level rises.
Higher levels of glycated hemoglobin in diabetes have been linked to cardiovascular disease, nephropathy, neuropathy, and other complications.
The name HbA1c comes from the cation exchange chromatography separation of hemoglobin type A. HbA0 was given to the first fraction to separate, which was probably thought to be pure hemoglobin A. HbA1a, HbA1b, and HbA1c were given to the subsequent fractions in the order in which they were eluted.
Huisman and Meyering used a chromatographic column to isolate hemoglobin A1c from other types of hemoglobin for the first time in 1958.
In 1968, Bookchin and Gallop classified it as a glycoprotein for the first time. Samuel Rahbar and colleagues initially noted the rise in diabetes in 1969. In 1975, Bunn and his colleagues described the processes that led to its creation.
Anthony Cerami, Ronald Koenig, and colleagues introduced the use of hemoglobin A1c for assessing the level of control of glucose metabolism in diabetic patients in 1976.
Why is it important for managing diabetes?
Cell membranes of red blood cells change as a result of glycated hemoglobin’s rise in highly reactive free radicals. As a result, blood viscosity and blood cell aggregation rise, impairing blood flow.
Glycated hemoglobin can also harm cells by causing inflammation, which leads to the development of atherosclerotic plaque (atheroma).
The amount of glucose that binds to hemoglobin in red blood cells increases with the duration of blood hyperglycemia, as does the amount of glycated hemoglobin.
A hemoglobin molecule becomes glycated and stays that way forever. Hence, a buildup of glycated hemoglobin inside the red cell represents the typical level of glucose the cell has been exposed to throughout its life cycle.
Glycated hemoglobin testing evaluates treatment efficacy by keeping track of long-term serum glucose control.
The A1c test measures the weighted average of blood glucose levels throughout the red blood cells’ lifetime 117 days for men and 106 days for women. As a result, the level of A1c is significantly influenced more by the glucose levels on days close to the test than by those on days further away.
Data from clinical practice showed a significant improvement in HbA1c levels 20 days following the initiation or intensification of treatment for diabetes.
What do HbA1c test results mean?
Depending on the analytical method, the subject’s age, and biological variance between individuals, laboratory results may vary.
Those with diabetes mellitus or other conditions that cause consistently high blood sugar have higher levels of HbA1c.
Treatment objectives for diabetes patients might vary, but many of them include a target range of HbA1c levels. An HbA1c level that is close to or within the reference range is indicative of a diabetic with good glucose management.
HbA1c values below 6.5% are advised by the International Diabetes Federation and the American College of Endocrinology, however, the American Diabetes Association advises HbA1c values below 7.0 % for the majority of patients.
Patients with an HbA1c greater than 6.5 % had an increased risk of death, according to a retrospective study of type 2 diabetes patients aged 50 and older.
Consistently high blood sugar levels and, consequently, HbA1c)raise the risk of long-term vascular consequences of diabetes, such as gastroparesis, gangrene, coronary disease, heart attack, stroke, heart failure, kidney failure, blindness, and erectile dysfunction.
Moreover, the risk of immediate postoperative problems including slow wound healing is increased by poor blood glucose control.
Those with conditions that cause premature red blood cell death, such as glucose-6-phosphate dehydrogenase deficiency, sickle cell disease, or any other ailment, can have lower-than-expected levels of HbA1c.
Red blood cells will be quickly replaced by newly produced ones after blood donation. HbA1c will overestimate the real average levels because these additional RBCs will have only been present for a brief length of time.
In several situations, such as those involving blood loss, surgery, blood transfusions, anemia, high erythrocyte turnover, chronic renal or liver disease, the administration of large doses of vitamin C, or erythropoietin therapy, the results may not be accurate.
The typical reference range found in healthy young people is between 4.9 and 5.2%.
How are HbA1c levels interpreted?
The monitoring of blood sugar control in individuals with more high levels, known as diabetes mellitus, as well as those who may be prediabetic, is advised by glycated hemoglobin testing.
It offers significantly more illuminating data on glycemic behavior for a single blood sample than a fasting blood sugar reading. However, while choosing a course of treatment, fasting blood sugar testing is essential.
Similar to other guidelines, the American Diabetes Association recommends that the glycated hemoglobin test be carried out quarterly in patients with diabetes whose therapy has changed or who are not meeting glycemic goals and at least twice a year in patients with diabetes who are meeting treatment goals and who have stable glycemic control.
When a dietary or medical treatment adjustment has been made within the last six weeks, a glycated hemoglobin measurement is not acceptable.
The HbA1c test is not appropriate for individuals with recent blood loss, hemolytic anemia, or genetic variations in the hemoglobin molecule (hemoglobinopathy), such as sickle-cell disease and other diseases.