HbA1C test for Diabetes

Context (TH): A nationwide study published in 2023 estimates that India has 10.13 crore people with diabetes and 13.6 crore pre-diabetic people.
Additionally, over 35% of Indians suffer from hypertension, and nearly 40% have abdominal obesity, both of which are risk factors for diabetes.
India accounts for 17% of all diabetes patients worldwide.
The HbA1C test or haemoglobin A1C, is widely used to diagnose pre-diabetes and diabetes, including both type 1 and type 2.
The HbA1C test, also known as the glycated haemoglobin or glycosylated haemoglobin test, is valuable in managing diabetes effectively.

Though HbA1c was first discovered in 1955. Standardisation and accuracy of HbA1c measurements greatly improved from 1993 to 2012.
The American Diabetes Association approved HbA1c as a diagnostic tool in 2009.
In 2011, the WHO stated that HbA1c could be used as a diagnostic test for diabetes under certain conditions.

How does the HbA1C test work?

Sugar from the food you eat enters your bloodstream.
This sugar, called glucose, attaches to the haemoglobin in your red blood cells.
- Haemoglobin is a protein that carries oxygen to all your body’s cells.
Everyone has some sugar attached to their haemoglobin. People with pre-diabetes and diabetes have more sugar attached.
The HbA1C test measures the percentage of red blood cells that have sugar-coated, or glycated, haemoglobin.

HbA1C levels are provided as either a percentage or in mmol/mol.
A higher percentage indicates higher blood glucose levels.
No diabetes HbA1C levels are below 5.7%.
Pre-diabetes Levels between 5.7 and 6.4%.
Diabetes: A percentage of 6.5% or higher.
In mmol/mol, below 42 corresponds to below 6.0%, 42-47 mmol/mol to 6.0 to 6.4%, and 48 mmol/mol to 6.5% or over.
Limitations
- Certain conditions, including kidney or liver failure, severe anaemia, blood disorders, and certain medications, can affect test results.
- Medications like steroids, opiates, or dapsone can also impact results.
- Results may change during early or late pregnancy.
- While the HbA1C test is useful for assessing long-term diabetes control, it’s not universally accepted as a diagnostic test due to assay standardisation issues.
- Doctors may recommend glucose tests alongside HbA1C tests for a clearer diagnosis.

For the Management of Type 2 Diabetes (2018), all individuals older than 30 years should be screened for diabetes.
Those with one or more risk factors, such as obesity, increased waist circumference, history of or treatment for hypertension, history of heart disease, or history of polycystic ovarian syndrome, should be screened earlier.

It should be conducted after three years for individuals with normal glucose tolerance.
If a person is pre-diabetic, retests should be done annually.
Doctors may recommend more frequent testing, especially for individuals planning to have a baby.
For those with diabetes, doctors may advise testing every three to six months to monitor blood sugar levels and assess the effectiveness of the treatment plan.

Fasting and post-prandial blood sugar tests provide blood sugar levels within a specific time frame. In contrast, the HbA1C test reflects average blood glucose levels over the last two to three months.
Traditional blood sugar tests may fluctuate based on recent meals and consumption timing. However, the HbA1C test is not affected by these variables, making it more reliable. It can be taken regardless of when the last meal was consumed.

The HbA1C test should not replace other tests for diabetes diagnosis but can be used alongside traditional blood sugar tests.
Home blood sugar testing is still necessary as it captures fluctuations that the HbA1C test may miss.
In India, the test may be limited by conditions like thalassaemia, haemoglobin variants, iron deficiency anaemia, and certain medications. Alternative tests are needed in cases where HbA1C levels are affected by these conditions.

Glucose: Our bodies use glucose for energy. Glucose, a type of sugar, comes from two places: Food and liver.
Insulin: Insulin, a hormone, helps move glucose from our blood to the cells, which then use the sugar for energy. Without insulin, glucose stays in your blood, and person can’t use that energy.
Pancreas: This organ creates the insulin your body needs to get and use glucose.
Islet Cells: These cells make insulin in your pancreas. Your pancreas has other functions that can continue, even if your islet cells fail to create insulin.
Type 1 vs Type 2 Diabetes
- In diabetes type 1, the pancreas does not make insulin because the body’s immune system attacks the islet cells in the pancreas that make insulin. (An Autoimmune Disease).
- In diabetes type 2, the pancreas makes less insulin than used to, and your body becomes resistant to insulin. This means your body has insulin but stops being able to use it.it is related to having too much body fat.