Glucose-Derived Personalized HbA1c Correction (GDAC) Study to Improve Alignment Between CGM-Derived Metrics and HbA1c in Different Individuals and Racial Groups With Diabetes: Implications for Clinical Practice

OBJECTIVE: Glycated hemoglobin (HbA1c) and average glucose (AG) can show discordance due to personal variations in red blood cell (RBC) physiology, creating management difficulties. Our aims were to understand the size of the problem and refine this glycemic metric by adjusting for personal differences in RBC characteristics. RESEARCH AND DESIGN AND METHODS: A 26-week prospective study was conducted in individuals with type 1 diabetes (T1D) or type 2 diabetes across four racial groups with HbA1c collected every 2 weeks and continuous glucose monitoring (CGM) used throughout. Personal glycation ratio (PGR) was derived from HbA1c and AG data (weeks 0-12), allowing calculation of personalized HbA1c (pA1C) and subsequent testing (weeks 20-26). The relationship between AG and HbA1c or pA1C was then analyzed, documenting a clinically meaningful discordance of ≥0.5%. In addition, we used real-world data sets to further validate the accuracy of pA1C at reflecting glucose exposure. RESULTS: Of 257 participants (19% T1D) with complete CGM and HbA1c data sets, mean age (±SD) was 53 ± 14 years (45% females). The racial background was 35% Asian, 30% White, 22% Black, and 14% other/mixed. Of the total study population, 33% showed ≥0.5% HbA1c-AG discordance, with the Black population affected most (41% discordance). Use of pA1C reduced the discordance in the whole population to 14% (58% reduction), while this was reduced in the Black population to 12% (71% reduction). CONCLUSIONS: HbA1c-AG discordance is common, particularly in the Black population, with pA1C improving alignment with glucose levels, potentially helping to optimize clinical management and reduce health disparities.