Department of Chemical Pathology, School of Medicine, Sefako Makgatho Health Sciences University, Pretoria, South Africa; National Health Laboratory Service, Dr George Mukhari Academic Hospital, Pretoria, South Africa.
S Afr Med J. 2020 Apr 29;110(5):416-421. doi: 10.7196/SAMJ.2020.v110i5.13959.
Glycated haemoglobin (HbA1c) has been used for decades as a measure of chronic glycaemia. A simple linear relationship between HbA1c values and mean blood glucose (MBG) has been identified and led to conversion of HbA1c values into estimated average glucose (eAG) levels, following the findings of the A1c-Derived Average Glucose (ADAG) Study Group. The intention was to help patients with diabetes mellitus (DM) understand their glycaemic control better, as eAG is reported in the same units as self-monitored glucose levels. However, factors other than glycaemia have been found to affect the relationship between HbA1c and MBG.
To: (i) determine the relationship between self-monitored MBG levels and HbA1c values; and (ii) evaluate the correlation between MBG levels and eAG levels calculated from HbA1c values using the regression equation derived from the ADAG Study Group in black South African patients with DM.
This was a prospective observational study of 96 diabetic patients. MBG levels were calculated using glucose measurements downloaded from the glucose meters for the previous 90 days (3 months). High-performance liquid chromatography was used for measurement of HbA1c values, collected at the end of 3 months. eAG was calculated using the regression equation from the ADAG Study Group, as follows: eAG (mmol/L) = 1.5944 × HbA1c (NGSP, %) - 2.594.
A positive correlation was found between MBG and HbA1c in all participants (R2=0.69, p<0.0001). There was a wide range of MBG levels for any given HbA1c value. Clinically significant differences between MBG and eAG were found, with a ≥10% difference in 65.6% of the participants. eAG overestimated MBG in ~71.8% of the study population, with an overestimation of ≥1.6 mmol/L (28.7 mg/dL, equivalent to a 1% change in HbA1c value) in ~50% of the total study population.
Our findings showed an imperfect relationship between MBG levels and HbA1c values. eAG significantly overestimated MBG, and this disagreement may cause confusion among both patients and clinicians. The risk of hypoglycaemic episodes may also increase if HbA1c and eAG alone are used to intensify therapy. We recommend that the use of eAG should be validated prior to implementation in clinical practice. It would be ideal to evaluate the relationship between average glucose and HbA1c in each individual patient in order to provide more personalised diabetes care.
糖化血红蛋白（HbA1c）已被用于衡量慢性血糖水平数十年。ADAG 研究小组发现，HbA1c 值与平均血糖（MBG）之间存在简单的线性关系，从而将 HbA1c 值转换为估算平均血糖（eAG）水平。其目的是帮助糖尿病患者更好地了解他们的血糖控制情况，因为 eAG 的报告单位与自我监测的血糖水平相同。然而，除了血糖之外，其他因素也被发现会影响 HbA1c 和 MBG 之间的关系。
（i）确定自我监测的 MBG 水平与 HbA1c 值之间的关系；（ii）评估使用 ADAG 研究小组回归方程计算的 HbA1c 值与 eAG 水平之间的相关性，在南非黑人糖尿病患者中。
这是一项对 96 名糖尿病患者的前瞻性观察研究。MBG 水平使用过去 90 天（3 个月）从血糖仪下载的血糖测量值计算得出。HbA1c 值使用高效液相色谱法测量，在 3 个月结束时收集。使用 ADAG 研究小组的回归方程计算 eAG，如下所示：eAG（mmol/L）=1.5944×HbA1c（NGSP，%）-2.594。
在所有参与者中，MBG 与 HbA1c 之间均呈正相关（R2=0.69，p<0.0001）。对于任何给定的 HbA1c 值，MBG 水平的范围都很广。MBG 和 eAG 之间存在显著的临床差异，65.6%的参与者差异≥10%。eAG 高估了约 71.8%的研究人群中的 MBG，约 50%的总研究人群中高估≥1.6mmol/L（28.7mg/dL，相当于 HbA1c 值变化 1%）。
我们的研究结果表明，MBG 水平与 HbA1c 值之间的关系并不理想。eAG 显著高估了 MBG，这可能会导致患者和临床医生产生混淆。如果单独使用 HbA1c 和 eAG 来加强治疗，低血糖发作的风险也可能增加。我们建议在临床实践中实施之前验证 eAG 的使用。理想情况下，应在每个个体患者中评估平均血糖与 HbA1c 之间的关系，以提供更个性化的糖尿病护理。
