A new study by Lancet Regional Health points out that the widely used glycated haemoglobin (HbA1c) test for monitoring and diagnosis of type-2 diabetes might not be reliable for the Indian population. The study said that in South Asia, particularly India, the high prevalence of anemia, hemoglobinopathies, and red blood cell enzyme (G6PD) deficiency coupled with poorly-standardised HbA1c test methods raises doubts on its reliability to treat diabetes.
“Its widespread use – and the tendency toward oversimplification by both physicians and patients – can lead to misinterpretation. The assumption that HbA1c uniformly reflects glycemic control across all individuals, regardless of genetic, hematologic, or metabolic variation, is increasingly difficult to justify in some populations, such as Asian Indians,” the study noted.
What does Lancet’s study recommend?
Lancet’s study, authored by four doctors, has cautioned that relying on HbA1c to diagnose prediabetes or diabetes in iron-deficient populations may lead to overestimation of disease prevalence.
“These findings underline the need for caution in relying solely on HbA1c in Asian Indian populations, where hematological abnormalities are common, and reinforces the value of oral glucose tolerance test (OGTT) as a confirmatory diagnostic tool in these settings,” the study stated.
Most clinicians rely on HbA1c for the diagnosis and management of type-2 diabetes. Its practical advantages are well known such as the test does not require fasting, reflects glycemic trends over the preceding 2-3 months, and has been broadly adopted in clinical guidelines, including those of the World Health Organisation (WHO) and the American Diabetes Association (ADA).
Additionally, the findings suggest that the reliability of HbA1c as a marker varies based on whether it is being used for diagnosis or for monitoring.
In case of diagnosis, for instance, conflicting results lead to misclassification of diabetes status, especially in individuals with coexisting conditions like anemia. During monitoring, misleading results could obscure short-term glycemic fluctuations or treatment responses.
Seasonal variations in HbA1c levels
Interestingly, seasonal variations in HbA1c levels have also been seen in Indians. A study of 8,138 Indian patients found seasonal variations in HbA1c levels with peaks during the monsoon (June–September) and the lowest levels in autumn (October–November). Patients with well-controlled diabetes exhibited higher HbA1c levels during winter and the monsoon, whereas those with elevated HbA1c showed lower values during the monsoon and autumn.
“Prevalence data from India should not rely solely on HbA1c, as doing so may lead to overestimation of prediabetes and diabetes. In urban settings, primary care physicians should ensure HbA1c tests are performed using validated methods and interpreted together with c complete blood count (CBC) and clinical history. A simple and accurate diagnostic test should be developed for India, building on previous efforts made in this direction,” the study said.