HbA1C test for diabetes

News Excerpt:

According to 2018 ICMR guidelines, everyone older than 30 years should be screened for diabetes.

Current status of diabetes in India:

  • India is estimated to have 10.13 crore people with diabetes, and another 13.6 pre-diabetic crore people, according to a nationwide study published in 2023. 
  • This apart, over 35% of Indians suffer from hypertension and nearly 40% from abdominal obesity, both of which are risk factors for diabetes. 
  • India accounts for 17% of all diabetes patients in the world.

What Is Diabetes?

  • Diabetes is a disease that occurs when your blood glucose, also called blood sugar, is too high. 
    • Glucose is the body's main source of energy. The body itself makes glucose and it also comes from the food you eat.
  • Insulin is a hormone made by the pancreas that helps glucose get into your cells to be used for energy. 
    • If one has diabetes, the body doesn’t make enough or any insulin, or doesn’t use insulin properly. Glucose then stays in your blood and doesn’t reach your cells.
  • Diabetes raises the risk of damage to the eyes, kidneys, nerves, and heart. It is also linked to some types of cancer. 

About the HbA1C test for Diabetes:

  • One of the most commonly-used tests to diagnose pre-diabetes and diabetes (both type 1 and type 2) and to help manage diabetes, is the haemoglobin A1C (HbA1C) test.
    • It is also known as the glycated haemoglobin or glycosylated haemoglobin test.
  • The HbA1C test measures the percentage of red blood cells that have sugar-coated, or glycated, haemoglobin.
    • Everybody has some sugar attached to their haemoglobin. Those with pre-diabetes and diabetes, however, have more. 
  • The importance of precise HbA1c measurements became apparent through studies that revealed better patient outcomes and mortality associated with lower average HbA1C.
  • Following programmes to regulate HBA1C measurements and calibrate them to reference standards, standardisation and accuracy greatly improved from 1993 to 2012.
  • The American Diabetes Association approved HbA1C as a diagnostic tool in 2009. 
  • In 2011, after an expert consultation with the World Health Organisation (WHO), it said HbA1C could be used as a diagnostic test for diabetes “provided stringent quality assurance tests are in place”.
  • While the traditional blood sugar tests may fluctuate depending on items in the person’s latest meal and when they last consumed it, the HbA1C test is independent of these variables, making it more reliable. 

What do HbA1C test results look like?

  • The HbA1C levels are provided as either a percentage or in mmol/mol (which stands for millimoles per mole). 
    • A mole is a unit of measurement often used for chemical substances.
  • The higher the percentage, the higher your blood glucose levels are. 
  • An Hb1A1C below 5.7% is considered normal; between 5.7 and 6.4% may indicate you are pre-diabetic; and 6.5% or higher can indicate diabetes. 
  • 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.
  • The test’s results may change under certain conditions, including: -  
    • If a patient has kidney or liver failure, severe anaemia or a blood disorder such as thalassemia; 
    • If they have a less common type of haemoglobin found in some populations; or are under certain medications including steroids, opiates or dapsone (a drug used to treat leprosy). 
    • They may even change if a person is in early or late pregnancy.
    • HbA1C levels vary from person to person and also depend on their age, health conditions, medications being taken, and other factors.

Who needs to take the test and when?

  • According to the Indian Council of Medical Research’s Guidelines for Management of Type 2 Diabetes (2018), all individuals older than 30 years should be screened for diabetes. 
  • Those with one or more risk factors including: - 
    • Obesity,
    • An increased waist circumference, 
    • A history of or being treated for hypertension
    • A history of heart disease, and 
    • A history of polycystic ovarian syndrome should be screened earlier.
  • Retests should be conducted after three years in case of normal glucose tolerance. If a person is pre-diabetic, retests should be annual. 
  • Doctors may also ask to be tested more frequently if, for instance, one is planning to have a baby.
  • If one has diabetes, his/her doctor may ask to take it every three to six months, to check blood sugar levels and to check if the treatment plan is working.

What are the test’s limitations?

  • The HbA1C test does not replace other tests and may be carried out alongside the traditional blood sugar tests to test for diabetes and pre-diabetes. 
  • It is not uniformly accepted as a diagnostic test by all global medical bodies because of its relatively low sensitivity arising from difficulties in assay standardisation. 
    • A doctor may recommend a glucose test alongside an HbA1C test to obtain a clearer picture when diagnosing a person.
  • In some clinical situations, accurate measurements are harder to make by this test like:
    • Thalassaemia,
    • Structural haemoglobin variants in the population, 
    • Iron deficiency anaemia (relatively high in India), and 
    • The use of certain drugs.
  • In the case of India, where frequent occurrence of some of these above conditions in some parts of India, it is important that they are looked for when evaluating an inappropriately high or low HbA1C level. Alternative indices may have to be used for assessing glycemic control in these cases.

The HbA1C test is a crucial tool for diagnosing and managing diabetes, offering reliable results unaffected by recent meals. Despite its advantages, it's not universally accepted due to assay standardization issues and limitations in certain conditions. Doctors may recommend additional tests for a comprehensive diagnosis, especially in regions like India with specific population health challenges.

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