HbA1c is a laboratory test that shows the average level of blood glucose over the previous 3 months and how well a diabetic patient is controlling the sugars.
How is the HbA1c test carried out?
The blood specimen is obtained in two ways either by venipuncture or finger stick.
HbA1c may be separated by charge and size from the other hemoglobin A components in blood by high-pressure liquid chromatography (HPLC). Here blood is separated into its various components by addition of mixtures to special liquids and then passing them under pressure through columns which then separates it into its different component molecules.
Because HbA1c is not affected by short-term fluctuations in blood glucose concentrations. Fasting for the blood test is not necessary.
Basic Physiology Behind The Test
Red cells have hemoglobin responsible for oxygen transport. About 90% of hemoglobin is hemoglobin A which is the adult type of hemoglobin. Hemoglobin type A is made up of 4 minor hemoglobin components. These components are slightly different chemically s. They include hemoglobin A1c, A1b, A1a1, and A1a2.
Hemoglobin A1c (HbA1c) is a minor component of hemoglobin to which glucose is bound. HbA1c also is sometimes referred to as Glycated hemoglobin is known as A1c. (C for carbohydrate), glycosylated hemoglobin, or glycohemoglobin.
When there are high levels of glucose there is more binding of this glucose to the hemoglobin and when measured in percentage it is known as HbA1c or percentage HbA1c.
Hemoglobin A1c test depends on the chemical charge on the HbA1c molecule which is different from the charges on the other three components of hemoglobin (A1b, A1a1, A1a2).
Red blood cells carry the memory of that glucose in the form of A1c. This constantly changes as the RBCs keep on changing with the new RBCs. As the lifespan of the RBCs is 3-4 months that is 120 days on average then the RBCs will carry that memory for the last 3 months.
HbA1c, therefore, helps to identify Age accelerating glycation reactions in the body.
The test is indicated for all diabetics.
It is the Gold standard test to measure glucose control for the last 3 to 4 months.
It can also be used in diabetes diagnosis.
It assesses the relative risk of diabetes.
Results and interpretation
- The value below 5.6% is normal.
- Values between 5.7-6.4% indicate pre-diabetes whereas,
- Values from 6.5% or higher indicate diabetes.
Fasting plasma glucose or random blood glucose just gives a snapshot and not overall you about the diabetic state. Therefore it will not measure the severity and control of diabetes.
For any non-diabetic individual, the goal is to maintain HbA1c levels close to or even less than 5%.
In diabetic patients, the goal is to keep the levels below 7%.
The test may be incorrect in patients with
- Kidney disease
- chronic excessive alcohol intake,
- Vitamin C and E can cause a falsely low HbA1C level because of there inhibition of the glucose and hemoglobin binding.
Medical conditions that may falsely decrease HbA1c include
- Acute or chronic blood loss,
- Sickle cell disease,
When there high HbA1C levels, They mean that one is at risk of developing
- Eye disease-retinopathy.
- Heart disease.
- Kidney disease-nephropathy.
- Nerve damage-neuropathy.