Lancet Study Warns HbA1c Testing May Mislead Diabetes Diagnosis in India

Lancet Study Raises Concerns Over HbA1c-Based Diabetes Assessment

A study published in The Lancet Regional Health has drawn attention to potential limitations in the widespread use of glycated haemoglobin (HbA1c) testing for diagnosing and monitoring type-2 diabetes in India. Researchers caution that HbA1c values may not always represent actual blood glucose exposure in diverse Indian populations, potentially affecting both clinical decisions and national disease estimates.

Biological Factors Influencing HbA1c Accuracy

HbA1c serves as a long-term marker of glycaemic control by measuring haemoglobin glycation over the average lifespan of red blood cells (RBCs). While globally accepted as a standard diagnostic tool, its reliability depends on normal RBC turnover and haemoglobin integrity.

The study highlights several prevalent Indian health conditions that may distort HbA1c readings:

• Iron-deficiency anaemia

• Haemoglobinopathies (including thalassemia traits)

• Red blood cell enzyme disorders , notably glucose-6-phosphate dehydrogenase (G6PD) deficiency

Such conditions alter RBC lifespan or haemoglobin structure, leading to HbA1c values that may not correspond with true glucose levels.

Diagnostic Risks and Delayed Detection

Researchers warn that exclusive dependence on HbA1c testing can produce diagnostic inaccuracies. Both underestimation and overestimation of glycaemic status are possible.

Particularly significant is the effect of G6PD deficiency , where shortened RBC survival may artificially lower HbA1c despite elevated plasma glucose. This discrepancy may delay diagnosis and treatment initiation, increasing the likelihood of long-term complications.

Experts involved in the study emphasised that some patients could be diagnosed years later than clinically appropriate, while others may face unnecessary therapeutic interventions.

Regional Vulnerabilities and Systemic Challenges

The study notes that diagnostic distortions are more pronounced in rural and tribal regions where:

• Anaemia prevalence remains high

• Genetic blood disorders are relatively common

• Access to standardised laboratory infrastructure is uneven

Even in urban tertiary care hospitals, HbA1c interpretation may be influenced by unrecognised haematological variations. Additionally, inconsistencies in laboratory calibration and quality control were identified as critical factors affecting test accuracy.

Need for India-Specific Diagnostic Strategies

Recognising India’s unique epidemiological and biological landscape, researchers propose a resource-adapted diagnostic framework.

In Resource-Constrained Settings

• Greater reliance on Oral Glucose Tolerance Test (OGTT)

• Use of Fasting Plasma Glucose (FPG)

• Basic screening for anaemia where feasible

In Advanced Clinical Settings

• Combined application of HbA1c + OGTT