Data show race difference in relationship between glucose management indicator, HbA1c
Continuous glucose monitor data show a greater difference between HbA1c and the glucose management indicator metric for “non-white” vs. white adults with insulin-treated diabetes, which was also associated with higher risk for hypoglycemia.
The data from a single-center study, published in Diabetes Care, are consistent with data demonstrating HbA1c is higher among adults categorized as “non-white” (including American Indian or Alaska Native, Asian, Black, Native Hawaiian or Pacific Islander adults) vs. white adults for the same mean glucose level. Glucose management indicator (GMI) is a CGM-estimated HbA1c based on a formula derived from the regression line of mean glucose concentration points and HbA1c values. Data from 14 to 30 days can be used to calculate GMI.
“A clinically significant difference between laboratory HbA1c and GMI ( 0.5%) was observed more frequently in the non-white than white cohort,” Elena Toschi, MD, assistant professor of medicine at Harvard Medical School and director of the young adult program at Joslin Diabetes Center, and colleagues wrote. “In addition, a relative difference of HbA1c greater than GMI by at least 0.5% was observed in 90% of the non-white cohort compared with 75% of the white cohort and was strongly associated with higher time spent in hypoglycemia in the non-white cohort only. To our knowledge, this is the first time that the relationship between HbA1c and GMI in a population of different races has been described.”
In a retrospective study, Toschi and colleagues analyzed CGM metrics for 316 adults with diabetes using insulin, including 55% with type 2 diabetes (mean age, 60 years; 51% women; mean diabetes duration, 24 years). Insulin regimens included multiple daily injections (85%), insulin pump therapy (14%) and basal insulin only (< 1%). Researchers stratified participants by race as “non-white” (n = 68) and white (n = 248).
CGM metrics did not differ between the “non-white” and white groups, including time spent in the recommended glucose range of 70 mg/dL and 180 mg/dL (mean, 728 vs. 722 min/day), time spent in hypoglycemia below 70 mg/dL (median, 63 vs. 63 min/day) and GMI (mean, 7.7 vs. 7.6); however, mean HbA1c was higher for the non-white vs. the white cohort (8.7% vs. 8.1%; P = .01). The researchers found that an HbA1c higher than GMI by at least 0.5% was more common for the “non-white” cohort (90% vs. 75%; P = .02). Additionally, in the “non-white” cohort only, duration of hypoglycemia was longer among those with HbA1c higher than GMI by at least 0.5% compared with those with HbA1c and GMI within 0.5%.
“The identified discrepancy between HbA1c and GMI and its strong correlation with time spent in hypoglycemia in the non-white cohort highlight the additional value of the use of CGM in non-white individuals with diabetes, in whom HbA1c tends to run higher than GMI,” the researchers wrote. “Obtaining CGM-derived metrics, along with the measurement of HbA1c in non-white individuals with diabetes receiving insulin therapy, can help to establish the relationship between GMI and HbA1c. This relationship remains constant over time within a patient and can guide clinicians to develop a personalized patient-centric treatment plan that may allow a higher HbA1c goal in some non-white individuals in order to avoid hypoglycemia.”