Racial differences in measures of glycemia in the Vitamin D and Type 2 Diabetes (D2d) Study: a secondary analysis of a randomized trial

Introduction Understanding how race may influence the association between A1c and glycemia can improve diabetes screening. We sought to determine whether, for a given A1c level, glucose levels during an oral glucose tolerance test (OGTT) differed by race. Research design and methods From data collected at 22 US clinical sites, we conducted a cross-sectional study of concurrently measured A1c and OGTT and observational longitudinal follow-up of the subset with high-risk pre-diabetes. Numerical integration methods were used to calculate area under the glycemic curve (AUCglu) during OGTT and least squares regression model to estimate A1c for a given AUCglu by race, controlling for potential confounders. Results 1016 black, 2658 white, and 193 Asian persons at risk of diabetes were included in cross-sectional analysis. Of these, 2154 with high-risk pre-diabetes were followed for 2.5 years. For a given A1c level, AUCglu was lower in black versus white participants. After adjustment for potential confounders, A1c levels for a given AUCglu quintile were 0.15–0.20 and 0.02–0.19 percentage points higher in black and Asian compared with white participants, respectively (p<0.05). In longitudinal analyses, black participants were more likely to be diagnosed with diabetes by A1c than white participants (28% vs 10%, respectively; p<0.01). Black and Asian participants were less likely to be diagnosed by fasting glucose than white participants (16% vs 15% vs 37%, respectively; p<0.05). Black participants with A1c levels in the lower-level quintiles had greater increase in A1c over time compared with white participants. Conclusions Use of additional testing beyond A1c to screen for diabetes may better stratify diabetes risk in the diverse US population.

引言 了解种族如何影响糖化血红蛋白（A1c）与血糖之间的关联可以改进糖尿病筛查。我们试图确定在给定的A1c水平下，口服葡萄糖耐量试验（OGTT）期间的血糖水平是否因种族而异。 研究设计与方法 从美国22个临床站点收集的数据中，我们对同时测量的A1c和OGTT进行了一项横断面研究，并对患有高危糖尿病前期的亚组进行了观察性纵向随访。采用数值积分方法计算OGTT期间的血糖曲线下面积（AUCglu），并使用最小二乘回归模型按种族估计给定AUCglu对应的A1c，同时控制潜在的混杂因素。 结果 1016名黑人、2658名白人和193名有糖尿病风险的亚洲人被纳入横断面分析。其中，2154名患有高危糖尿病前期的患者被随访了2.5年。在给定的A1c水平下，黑人参与者的AUCglu低于白人参与者。在对潜在混杂因素进行调整后，给定AUCglu五分位数下，黑人参与者和亚洲参与者的A1c水平分别比白人参与者高0.15 - 0.20和0.02 - 0.19个百分点（p < 0.05）。在纵向分析中，黑人参与者通过A1c被诊断为糖尿病的可能性高于白人参与者（分别为28%对10%；p < 0.01）。黑人和亚洲参与者通过空腹血糖被诊断的可能性低于白人参与者（分别为16%对15%对37%；p < 0.05）。与白人参与者相比，A1c水平处于较低五分位数的黑人参与者随着时间推移A1c的升高幅度更大。 结论 在美国多样化的人群中，使用A1c之外的其他检测方法来筛查糖尿病可能更好地对糖尿病风险进行分层。