Ethnicity modifies link between HbA1c and FPG in Asian populations

3 February 2012

MedWire News: The use of glycated hemoglobin (HbA1c) in place of fasting plasma glucose (FPG) as an indicator for glycemic status will reclassify Asian individuals’ diabetes status differently depending on their ethnicity, show study findings.

“Delineating ethnic differences in the relationship between FPG and HbA1c is especially important in Asian populations, given that the prevalence of cases of diabetes in this region is projected to more than double by 2030,” write Eric Khoo (National University of Singapore, Kent Ridge) and colleagues in Diabetic Medicine.

The findings come from the Singapore Prospective Study, which included 3895 individuals who completed a questionnaire to provide information on their demographics, lifestyle, and medical history, and underwent a health examination including anthropometric and biochemical assessment.

The majority (69.2%) of the participants were of Chinese ethnicity, 16.3% were Malaysian, and 14.5% were Indian.

The researchers found that, as mean FPG increased, the mean HbA1c level increased more in individuals of Malaysian and Indian ethnicity than it did in those of Chinese ethnicity.

The team estimated mean HbA1c values at FPG levels ranging from 4.0 to 7.5 mmol/L which showed that Malaysian and Indian individuals have lower HbA1c at lower FPG values and higher HbA1c at higher FPG values than Chinese individuals do, with a crossover at FPG 5.0 mmol/L.

The authors say their estimations translate to a difference in mean HbA1c of 0.10% between Indian and Chinese populations and of 0.08% between Malaysian and Chinese populations at an FPG level of 5.6 mmol/L, which is the American Diabetes Association (ADA) criterion for impaired fasting glucose.

And at an FPG of 7.0 mmol/L, the ADA criterion for diabetes, the difference in HbA1c between Indian and Chinese populations is 0.19% and between Malaysian and Chinese populations it is 0.24%, they report.

“Although the effect of ethnicity in HbA1c seems small, it may be significant if HbA1c is widely accepted and applied as a diagnostic tool in our population,” write Khoo et al.

“Further studies are required to understand the glycemic and nonglycemic effects of ethnicity on HbA1c and diabetes-associated complications, prior to determining whether ethnic-specific cut-offs for HbA1c are appropriate for the diagnosis of diabetes,” concludes the team.

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Diabet Med 2012; Advance online publication