Glycaemia-independent ethnic differences in HbA1c in subjects with impaired glucose tolerance

Aim To study the ethnic differences in HbA(1c) between Whites and South Asians with impaired glucose tolerance. Methods We audited 75g oral glucose tolerance tests (OGTT) performed in Clinical Chemistry, New Cross Hospital, Wolverhampton over 1 year. HbA(1c) and glycaemia were compared between Whites and South Asians with impaired glucose intolerance (IGT). Results There were 46 South Asians (22 female) and 88 Whites (41 female). South Asian subjects were younger (59.2 +/- 14.31 vs. 67.6 +/- 12.63 yrs; P < 0.001) and weighed less (78.1 +/- 17.2 vs. 87.47 +/- 19.1 kgs; P < 0.001) than White subjects. HbA(1c) levels were higher (6.5 +/- 0.7 vs. 6.1 +/- 0.6%; P < 0.001) in South Asians compared to Whites. Fasting glucose (5.71 +/- 0.5 vs. 5.93 +/- 0.7; P = 0.039) was lower in South Asians but 2hour glucose (10.5 +/- 1.0 vs. 10.40 +/- 0.9; P = 0.404) was similar in both ethnic groups. Conclusion South Asians have higher HbA(1c) levels than Whites despite lower fasting glucose value on OGTT, indicating ethnic differences in HbA(1c) are due to glycaemia-independent factors.