Estimated average glucose
Pro Research Analysisby 
Searched over 200M research papers
Consensus Meter
Understanding the Relationship Between Estimated Average Glucose and Fasting Plasma Glucose
Introduction to Estimated Average Glucose (eAG)
Estimated average glucose (eAG) is a value derived from hemoglobin A1c (HbA1c) levels, providing an estimate of the average blood glucose levels over the preceding few months. The International HbA1c-Derived Average Glucose (ADAG) Trial in 2008 established a linear relationship between HbA1c and eAG, which has since been widely adopted in clinical practice .
Correlation Between eAG and Fasting Plasma Glucose (FPG)
Several studies have explored the relationship between eAG and fasting plasma glucose (FPG). A retrospective study involving 6443 subjects, including both diabetic and non-diabetic individuals, found a moderate correlation between FPG and eAG (r=0.672, p<0.001). However, the strength of this correlation varied depending on the glycemic control of the subjects. For instance, in diabetic patients, the correlation decreased as FPG levels decreased (r=0.425 for FPG ≥10.0 mmol/L, r=0.202 for FPG <7.2 mmol/L). Similarly, non-diabetic subjects showed a weaker correlation at lower FPG levels (r=0.363 for FPG 5.6-6.9 mmol/L, r=0.186 for FPG <5.6 mmol/L).
Discrepancies Between eAG and Mean Blood Glucose (MBG)
Research has also highlighted discrepancies between eAG and mean blood glucose (MBG) levels. A study comparing eAG with MBG in type 1 diabetes patients found significant disagreement, with eAG overestimating or underestimating MBG by 28.7 mg/dL or more in about 33% of patients. This discrepancy was more pronounced at lower MBG levels, suggesting that eAG might not always accurately reflect actual glucose control.
Biological Variation and eAG Accuracy
The accuracy of eAG can be influenced by biological variations in the relationship between HbA1c and MBG. For example, a study involving pediatric type 1 diabetic patients found that eAG underestimated MBG in patients with low hemoglobin glycation index (HGI) and overestimated it in those with high HGI. This variation can lead to confusion in clinical practice if eAG is used without considering individual patient differences.
Special Considerations in Pregnancy
The relationship between HbA1c and average glucose levels is altered during pregnancy. A study on pregnant women with diabetes found that standard eAG values did not accurately reflect average glucose levels during pregnancy. Instead, a pregnancy-specific eAG (PeAG) was recommended, which accounted for the changes in glucose metabolism during gestation. This highlights the need for tailored eAG calculations in specific populations to ensure accurate monitoring and management of blood glucose levels.
Conclusion
The relationship between estimated average glucose (eAG) and fasting plasma glucose (FPG) is complex and influenced by various factors, including glycemic control and biological variations. While eAG provides a useful estimate of average glucose levels, discrepancies with mean blood glucose (MBG) and special considerations in populations such as pregnant women necessitate a cautious and customized approach in its clinical application. Understanding these nuances can enhance the effectiveness of diabetes management and improve patient outcomes.
Sources and full results
Most relevant research papers on this topic