Correlation between Estimated Average Glucose Levels Calculated from HbA1c Values and Random Blood Glucose Levels in a Cohort of Subjects

Objective Hemoglobin A1c (HbA1c) level remains the gold standard test for the assessment of glycemic control, and it reflects the mean glucose values in the previous 3-month period. HbA1c is expressed as a percentage, whereas the monitoring and treatment of diabetes are based on blood glucose levels expressed as mg/dL. It is appropriate to make it easy for the patient to understand both random blood sugar (RBS) and estimated average glucose (eAG) expressed with the same units. This will enhance the usefulness of eAG. This article determines the statistical correlation between eAG derived from HBA1C with RBS values both in diabetic and prediabetic subjects. Methods The RBS and HbA1c levels of 178 males and 283 females (12–90 years) were obtained and the eAG levels were calculated using Nathan's regression equation. The samples were divided into four groups based on HbA1c levels—group 1: HbA1c greater than 9%, group 2: HbA1c 6.5 to 9%, group 3: HbA1c 5.7 to 6.4%; and group 4: HbA1c less than 5.7%. Results There was a statistically significant positive correlation between RBS and eAG values for the study group 1 and 2. Also, the median values of RBS and eAG showed a significant difference ( p < 0.001). Conclusion As the association between the RBS and eAG levels is strong in a fairly and poorly controlled diabetic population, reporting the eAG level together with the HbA1c level at no additional cost may assist in effective blood glucose control in clinical care. However, eAG and RBS values cannot be used interchangeably.