OBJECTIVE To examine the accuracy of different periods of continuous glucose monitoring (CGM), hemoglobin A1c (HbA1c), and their combination for estimating mean glycemia over 90 days (AG90). RESEARCH DESIGN AND METHODS We retrospectively studied 985 CGM periods of 90 days with <10% missing data from 315 adults (86% of whom had type 1 diabetes) with paired HbA1c measurements. The impact of mean red blood cell age as a proxy for nonglycemic effects on HbA1c was estimated using published theoretical models and in comparison with empirical data. Given the lack of a gold standard measurement for AG90, we applied correction methods to generate a reference (eAG90) that we used to assess accuracy for HbA1c and CGM. RESULTS Using 14 days of CGM at the end of the 90-day period resulted in a mean absolute error (95th percentile) of 14 (34) mg/dL when compared with eAG90. Nonglycemic effects on HbA1c led to a mean absolute error for average glucose calculated from HbA1c of 12 (29) mg/dL. Combining 14 days of CGM with HbA1c reduced the error to 10 (26) mg/dL. Mismatches between CGM and HbA1c >40 mg/dL occurred more than 5% of the time. CONCLUSIONS The accuracy of estimates of eAG90 from limited periods of CGM can be improved by averaging with an HbA1c-based estimate or extending the monitoring period beyond ∼26 days. Large mismatches between eAG90 estimated from CGM and HbA1c are not unusual and may persist due to stable nonglycemic factors.

中文翻译：

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根据 HbA1c 和 CGM 估算血糖：准确性和差异来源分析

目的 检查不同时期的连续血糖监测 (CGM)、糖化血红蛋白 (HbA1c) 及其组合在估计 90 天平均血糖 (AG90) 方面的准确性。研究设计和方法 我们回顾性研究了 315 名成年人（其中 86% 患有 1 型糖尿病）的 90 天 985 个 CGM 周期，缺失数据 <10%，并进行了配对 HbA1c 测量。使用已发表的理论模型并与经验数据进行比较，估计了平均红细胞年龄作为非血糖效应对 HbA1c 的影响。鉴于 AG90 缺乏黄金标准测量，我们应用校正方法来生成参考 (eAG90)，用于评估 HbA1c 和 CGM 的准确性。结果 与 eAG90 相比，在 90 天周期结束时使用 14 天的 CGM 导致平均绝对误差（第 95 个百分位数）为 14 (34) mg/dL。对 HbA1c 的非血糖影响导致根据 HbA1c 计算的平均葡萄糖的平均绝对误差为 12 (29) mg/dL。将 14 天的 CGM 与 HbA1c 相结合，将误差降低至 10 (26) mg/dL。CGM和HbA1c>40mg/dL之间的不匹配发生率超过5％。结论 通过对基于 HbA1c 的估计值进行平均或将监测期延长至 26 天以上，可以提高有限 CGM 期间的 eAG90 估计值的准确性。根据 CGM 估计的 eAG90 与 HbA1c 之间存在较大不匹配并不罕见，并且由于稳定的非血糖因素可能会持续存在。