Age and Red Blood Cell Parameters Mainly Explain the Differences Between HbA1c and Glycemic Management Indicator
Pablo Azcoitia1, Raquel Rodríguez-Castellano1, Pedro Saavedra2
1Section of Endocrinology and Nutrition, Complejo Hospitalario Universitario Insular-Materno Infantil, Las Palmas de Gran Canaria, Spain.
Insights
Glycated hemoglobin (HbA1c) and glucose management indicator (GMI) often differ in patients with diabetes. Easily measured factors like age, mean corpuscular volume (MCV), and red cell distribution width (RDW) can help explain these glycemic control discrepancies.
Area of Science:
- Endocrinology
- Diabetes Management
- Clinical Chemistry
Background:
- Glycated hemoglobin (HbA1c) is the standard for assessing diabetes glycemic control.
- Glucose management indicator (GMI) from continuous glucose monitoring (CGM) is a proposed alternative.
- Discrepancies between HbA1c and GMI can complicate clinical decisions.
Purpose of the Study:
- To identify factors contributing to the difference between HbA1c and GMI.
- To improve the interpretation of glycemic control metrics in diabetic patients.
Main Methods:
- Retrieved HbA1c measurements and corresponding 14-day CGM data (Freestyle Libre 2) from 339 type 1 diabetes patients.
- Selected data with at least 70% CGM sensor usage.
- Collected clinical, glucometric, and laboratory data concurrent with HbA1c measurements.
Main Results:
- A significant difference between HbA1c and GMI (absolute difference <0.3%) occurred in only 38.7% of 646 paired measurements.
- Univariate analysis linked HbA1c-GMI differences to age, diabetes duration, eGFR, MCV, RDW, and time in range (180-250 mg/dL).
- Multilevel modeling identified age and RDW (positive correlation) and MCV (negative correlation) as significant predictors of HbA1c-GMI difference.
Conclusions:
- Clinically relevant differences between HbA1c and GMI are common.
- Age and hematological parameters (MCV, RDW) aid in interpreting HbA1c-GMI discrepancies.
- These factors can enhance the clinical utility of CGM-derived metrics.
Background:
Glycated hemoglobin (HbA1c) is the gold standard to assess glycemic control in patients with diabetes. Glucose management indicator (GMI), a metric generated by continuous glucose monitoring (CGM), has been proposed as an alternative to HbA1c, but the two values may differ, complicating clinical decision-making. This study aimed to identify the factors that may explain the discrepancy between them.
Methods:
Subjects were patients with type 1 diabetes, with one or more HbA1c measurements after starting the use of the Freestyle Libre 2 intermittent CGM, who shared their data with the center on the Libreview platform. The 14-day glucometric reports were retrieved, with the end date coinciding with the date of each HbA1c measurement, and those with sensor use ≥70% were selected. Clinical data prior to the start of CGM use, glucometric data from each report, and other simultaneous laboratory measurements with HbA1c were collected.
Results:
A total of 646 HbA1c values and their corresponding glucometric reports were obtained from 339 patients. The absolute difference between HbA1c and GMI was <0.3% in only 38.7% of cases. Univariate analysis showed that the HbA1c-GMI value was associated with age, diabetes duration, estimated glomerular filtration rate, mean corpuscular volume (MCV), red cell distribution width (RDW), and time with glucose between 180 and 250 mg/dL. In a multilevel model, only age and RDW, positively, and MCV, negatively, were correlated to HbA1c-GMI.
Conclusion:
The difference between HbA1c and GMI is clinically relevant in a high percentage of cases. Age and easily accessible hematological parameters (MCV and RDW) can help to interpret these differences.
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