Lancet Study Questions Reliability of HbA1c Testing for Diabetes Diagnosis in India

Lancet Study Flags Diagnostic Concerns Over HbA1c in India

A recent study published in The Lancet Regional Health has raised important concerns regarding the widespread dependence on glycated haemoglobin (HbA1c) testing for diagnosing and monitoring type-2 diabetes in India. The findings suggest that HbA1c values may not consistently reflect actual blood glucose levels across diverse Indian populations, potentially affecting both clinical diagnosis and national disease estimates.

Biological Factors Affecting HbA1c Accuracy

HbA1c measures the proportion of haemoglobin that has undergone glycation over the lifespan of red blood cells (RBCs), typically reflecting average glucose exposure over two to three months. However, the study highlights that variations in RBC lifespan, haemoglobin structure, or concentration can significantly influence HbA1c readings.

Conditions prevalent in India that may distort HbA1c include:

• Iron-deficiency anaemia

• Haemoglobinopathies (such as thalassemia traits)

• Enzyme deficiencies , notably glucose-6-phosphate dehydrogenase (G6PD) deficiency

These factors can lead to either artificially elevated or reduced HbA1c values, independent of true glycaemic status.

Implications for Diagnosis and Disease Burden Estimates

Researchers caution that exclusive reliance on HbA1c testing may contribute to diagnostic inaccuracies. In some individuals, diabetes detection may be delayed, while others may be incorrectly classified.

Particularly notable is the impact of G6PD deficiency , where shortened RBC lifespan can lower HbA1c values despite persistently high blood glucose. This mismatch can delay timely diagnosis and intervention, increasing vulnerability to complications.

The study also warns that large-scale epidemiological surveys using only HbA1c may misrepresent India’s actual diabetes prevalence.

Regional and Laboratory-Level Challenges

The diagnostic challenge is amplified in rural and tribal regions where:

• Anaemia prevalence remains high

• Genetic blood disorders are more common

• Laboratory standardisation may vary

Even in urban healthcare systems, RBC-related distortions may affect HbA1c interpretation. Additionally, inconsistencies in laboratory quality assurance frameworks were identified as a systemic concern influencing test reliability.

Call for Context-Specific Diagnostic Strategies

Recognising India’s unique population health profile, the study recommends a more adaptable diagnostic framework:

In Resource-Limited Settings

• Use of Oral Glucose Tolerance Test (OGTT)

• Fasting Plasma Glucose (FPG) measurements

• Basic haematological screening where feasible

In Advanced Healthcare Centres

• Combined use of HbA1c + OGTT

• Greater reliance on Continuous Glucose Monitoring (CGM)