Standard diabetes test glycated haemoglobin (HbA1c) may mislead in diagnosis of type-2 diabetes in India’s population: experts

Standard diabetes test glycated haemoglobin (HbA1c) commonly used to diagnose and monitor type-2 diabetes (T2D) may mislead diagnosis and monitoring in South Asia — particularly India’s population, with the high prevalence of anaemia, haemoglobinopathies (eg: sickle cell disease, thalassaemia), and glucose-6-phosphate dehydrogenase (G6PD) deficiency, noted an article published online in Lancet Regional Health: Southeast Asia.

Led by Anoop Misra, corresponding author and chairman of Fortis C-DOC Centre of Excellence for Diabetes, the review questions reliance on HbA1c as the sole diagnostic or monitoring tool for type-2 diabetes in South Asia.

The article adds that poorly standardised HbA1c assay methods complicate interpretation of HbA1c values. “Overall, reliance solely on HbA1c is constrained by several clinical and biological factors in India. A multiparametric, risk-stratified approach that integrates oral glucose tolerance test, self-monitoring of blood glucose, and whenever possible, continuous glucose monitoring, in addition to relevant hematologic assessments are essential to enhance diagnostic and monitoring accuracy and inform appropriate treatment decisions, especially in primary care and resource-limited settings,’’ said Dr. Misra.

Any condition that affects the quantity, structure, or lifespan of haemoglobin — such as anaemia, haemoglobinopathies, or other red blood cell disorders — can distort HbA1c values and lead to misleading estimates of average blood glucose, the viewpoint article notes.

Shashank Joshi, co-author from Joshi Clinic, Mumbai, explained that in some regions of India, people are nutritionally challenged and have iron-deficiency anaemia, which can distort HbA1c readings.

“This would affect both diagnosis and monitoring thus misleading clinicians. Reliance on HbA1c alone could delay diagnosis by up to four years in men with undetected G6PD deficiency, potentially increasing risk of complications,’’ said Dr. Joshi.

The article explained that in patients with type-1 diabetes, a non-linear relationship between mean blood glucose and HbA1c has been documented. Speaking on the article, diabetologist V. Mohan said that while HbA1c is the gold standard to understand control of diabetes, it cannot be the only test to diagnose diabetes and that this is not new information.

Rajeev Jayadevan, ex-president of Indian Medical Association, Cochin, added: “Studies from India have shown that correction of anaemia can reduce HbA1c level. Diagnosis of diabetes can’t be based on a single HbA1c value — the whole clinical picture must be considered,’’ he said.