Lancet Study Flags Limits of HbA1c Test in India

 New Delhi: A new evidence-based study published in The Lancet Regional Health – Southeast Asia has raised concerns over the accuracy of the glycated haemoglobin (HbA1c) test in diagnosing and monitoring Type 2 diabetes among large sections of India’s population.

The review, led by Anoop Misra and collaborators, found that HbA1c levels may not reliably reflect average blood glucose in individuals with conditions that affect red blood cells, including anaemia, haemoglobinopathies and glucose-6-phosphate dehydrogenase (G6PD) deficiency. These conditions are widely prevalent across many parts of India.

HbA1c reflects the degree of glycation of haemoglobin over time. The authors noted that disorders affecting the quantity, structure or lifespan of haemoglobin can distort HbA1c readings, leading to under- or over-estimation of blood glucose levels and potentially resulting in incorrect diagnosis or monitoring.

The study highlighted that iron-deficiency anaemia, which is common in nutritionally vulnerable populations in India, can significantly alter HbA1c values. Such distortions, the authors said, could mislead clinicians in both diagnosing diabetes and assessing long-term glycaemic control.

“Relying exclusively on HbA1c can result in misclassification of diabetes status,” Prof Misra, chairman of the Fortis C-DOC Centre of Excellence for Diabetes, said. He warned that delayed diagnosis, misdiagnosis and compromised monitoring could affect timely and effective diabetes management.

Co-author Shashank Joshi said HbA1c inaccuracies were observed even in well-equipped urban hospitals due to red blood cell variations and inherited blood disorders. He added that discrepancies were likely to be greater in rural and tribal regions, where anaemia and red cell abnormalities are more common.

The authors proposed a resource-adapted diagnostic and monitoring framework for India. In low-resource settings, they recommended the use of oral glucose tolerance tests (OGTT), involving fasting and two-hour post-glucose measurements, for diagnosis. For monitoring, they advised self-monitoring of blood glucose two to three times a week, along with basic haematological screening such as haemoglobin estimation and blood smear examination.

For tertiary care settings, the review suggested combining HbA1c testing, conducted with standardised equipment, with OGTT for diagnosis. For monitoring, it recommended continuous glucose monitoring along with alternative biochemical markers such as fructosamine.

The study concluded that while HbA1c remains a useful tool, it should not be used in isolation in populations with a high burden of red blood cell disorders, and diagnostic strategies need to be adapted to local health realities.

Why HbA1c fails

*Affected by: Anaemia, haemoglobinopathies, G6PD deficiency

*Common in India due to: Nutritional deficiencies, inherited blood disorders

What study recommends

*Low-resource settings: Oral Glucose Tolerance Test (OGTT), fasting + 2-hour glucose, self-monitoring of blood glucose (2–3 times/week), basic blood tests (haemoglobin, smear)