Abstract:
Aim: To determine whether there were ethnic differences in HbA1c concentrations in adults with normal and abnormal glucose tolerance. Methods: Cross-sectional data were from 3,559 participants not previously diagnosed with diabetes aged 35-74 years. Participants underwent a 75 gm oral glucose tolerance test. Glucose and fructosamine levels were determined enzymatically, and HbA1c by cation exchange high performance liquid chromatography. Results: Compared with Europeans, and after adjusting for age and gender, HbA1c levels were on average 5.5 (se=0.25) mmol/mol higher for Pacific, 2.5 (0.24) mmol/ mol higher for Māori, and 2.3 (0.40) mmol/mol higher for Asians. These ethnic differences were attenuated in a multivariable regression model for HbA1c, mainly due to the inclusion of current smoking habit and BMI, but still retained statistical significance. HbA1c levels were higher in Māori, Pacific and Asian participants with normal glycaemia, Māori and Pacific people with impaired fasting glycaemia, and impaired glucose tolerance, and Pacific people with newly diagnosed diabetes compared to Europeans after adjusting for age, gender, fasting and 2 hour glucose. Ethnic differences of HbA1c concentrations increased with increasing glycaemia compared to Europeans. After adjusting for age, gender and body mass index, the squared semi-partial correlations for HbA1c were 50.5% for fasting glucose and 3.6% for 2 hour glucose. Conclusions: HbA1c concentrations in this population mainly reflected fasting gluco