NEW DELHI: The widely used glycated hemoglobin (HbA1c) test - a standard diabetes test - may not accurately reflect blood glucose levels for millions of Indians, particularly in regions with high prevalence of anemia, hemoglobinopathies, and red blood cell enzyme (G6PD) deficiency, a latest Lancet study has said.
The study, published in the Lancet Regional Health-Southeast Asia, said the reliance on HbA1c alone could delay diagnosis by up to four years in men with undetected G6PD deficiency - a hereditary genetic disorder that affects red blood cells - potentially increasing risk of complications.
Questioning the reliance on HbA1c as a sole diagnostic or monitoring tool for type 2 diabetes in South Asia, especially India, the study said that in many cases, this should be combined with other tests for the diagnosis and monitoring of diabetes.
“Relying exclusively on HbA1c can result in misclassification of diabetes status,” said Prof. Anoop Misra, corresponding author and Chairman of Fortis C-DOC Center of Excellence for Diabetes.
“Some individuals may be diagnosed later than appropriate, while others could be misdiagnosed, which may affect timely diagnosis and management. Similarly, monitoring of blood sugar status may be compromised,” he said.
According to Dr. Shashank Joshi, co-author of the study, and endocrinologist from Joshi Clinic, Mumbai, “Even in well-resourced urban hospitals, HbA1c readings can be influenced by red blood cell variations and inherited hemoglobin disorders. In rural and tribal areas, where anemia and red cell abnormalities are common, the discrepancies may be greater.”
Dr. Shambho Samrat Samajdar, who is also co-author of the study, emphasized a comprehensive approach.
“Combining oral glucose tolerance test, self-monitoring of blood glucose, and hematologic assessments provides a more accurate picture of diabetes risk. This approach can help refine public health estimates and guide resource allocation," said Dr Samajdar, Diabetologist from the Department of Out-Patient Clinic, Diabetes and Allergy-Asthma Therapeutics Specialty Clinic, Kolkata.
The study said that in the Indian subcontinent, the rising number of people with type 2 diabetes (T2D) makes it essential to maintain good glycemic control to prevent a substantial burden of diabetes-related complications. It is imperative that T2D is properly diagnosed and monitored to reduce this burden and avoid adverse outcomes.
Further, accurate diagnosis is required for prediabetes and diabetes for appropriate management.
Due to this, most clinicians rely on glycated hemoglobin for the diagnosis and management of T2D.
The experts said the test is so common because it does not require fasting, reflects glycemic trends over the preceding two to three months, and has been broadly adopted in clinical guidelines, including those of the World Health Organization (WHO) and the American Diabetes Association.
“However, it is important to recognize that the clinical roles of HbA1c in diagnosing versus monitoring diabetes are distinct, and each may be affected differently by patient and laboratory factors.”
It said its widespread use - and the tendency toward oversimplification by both physicians and patients - can lead to misinterpretation, particularly in populations with altered erythrocyte dynamics, such as those with anemia or hemoglobinopathies.
The study concluded that the use of HbA1c as a standalone diagnostic or monitoring tool is often questionable in South Asian populations.
“Persistently high rates of anemia, inherited hemoglobin variants, enzymatic red cell disorders, and poorly standardized HbA1c measurement instruments can produce misleading values - leading to underdiagnosis, inappropriate treatment decisions, and delayed initiation of care. As India and neighboring countries expand their diabetes prevention and management programs, diagnostic algorithms must evolve toward more multiparametric, risk-stratified approaches that integrate clinical, biochemical, and hematologic data,” it added.
The study also said that in some regions of India, people are nutritionally challenged with many suffering from iron deficiency anemia, which can distort HbA1c readings.
It also highlighted that public health surveys based solely on HbA1c may misrepresent India’s diabetes burden.