Ethnicity modifies the relation between fasting plasma glucose and HbA1c in Indians, Malays and Chinese

Diabet. Med. 29, 911917 (2012) Abstract Aims To study whether HbA1c, and its relationship with fasting plasma glucose, was significantly different among Chinese, Malays and Indians in Singapore. Methods A sample of 3895 individuals without known diabetes underwent detailed interview and health examination, including anthropometric and biochemical evaluation, between 2004 and 2007. Pearsons correlation, analysis of variance and multiple linear regression analyses were used to examine the influence of ethnicity on HbA1c. Results As fasting plasma glucose increased, HbA1c increased more in Malays and Indians compared with Chinese after adjustment for age, gender, waist circumference, serum cholesterol, serum triglyceride and homeostasis model assessment of insulin resistance (P-interaction < 0.001). This translates to an HbA1c difference of 1.1 mmol/mol (0.1%, Indians vs. Chinese), and 0.9 mmol/mol (0.08%, Malays vs. Chinese) at fasting plasma glucose 5.6 mmol/l (the American Diabetes Association criterion for impaired fasting glycaemia); and 2.1 mmol/mol (0.19%, Indians vs. Chinese) and 2.6 mmol/mol (0.24%, Malays vs. Chinese) at fasting plasma glucose 7.0 mmol/l, the diagnostic criterion for diabetes mellitus. Conclusions Using HbA1c in place of fasting plasma glucose will reclassify different proportions of the population in different ethnic groups. This may have implications in interpretation of HbA1c results across ethnic groups and the use of HbA1c for diagnosing diabetes mellitus.