Glycated haemoglobin (HbA1c) test

The widely used glycated haemoglobin (HbA1c) test, considered the gold standard for diagnosing and monitoring Type-2 Diabetes (T2D), may produce misleading results in South Asian populations—particularly in India—due to the high prevalence of certain blood disorders, according to an article published in The Lancet Regional Health: Southeast Asia.

Researchers have flagged concerns that conditions such as anaemia, haemoglobinopathies (including sickle cell disease and thalassaemia), and glucose-6-phosphate dehydrogenase (G6PD) deficiency can distort HbA1c readings, potentially leading to under- or over-diagnosis of diabetes.

What is HbA1c?

HbA1c (glycated haemoglobin) measures the average blood sugar levels over the past two to three months. The test calculates the percentage of haemoglobin—the oxygen-carrying protein in red blood cells—that is bound to glucose.

• Below 5.7%: Normal
• 5.7%–6.4%: Prediabetes
• 6.5% and above: Diabetes

Since the association between blood glucose control and HbA1c levels was established in 1976, the test has become central to assessing long-term glycaemic control. In 2010, it was formally recommended as a diagnostic tool, largely due to its convenience.

Why It Became the Gold Standard

The HbA1c test offers several advantages:

• No fasting required, unlike traditional blood glucose tests
• Pre-analytical stability, meaning the sample remains reliable before testing
• Low intra-individual variability, providing consistent long-term assessment

Concerns in the Indian Context

However, experts note that HbA1c levels can be influenced by conditions that affect red blood cell lifespan or haemoglobin structure. In India and other South Asian countries, where anaemia and inherited blood disorders are relatively common, HbA1c values may not accurately reflect true blood glucose levels.

Source: TH