A labile form of hemoglobin A1c is higher in African‐American youth with type 1 diabetes compared to Caucasian patients at similar glucose levels

Abstract

Background Hemoglobin A1c (HbA1c) levels are higher in African‐American (AA) individuals compared to Caucasians (EA) even after adjustment for blood glucose levels. To better understand the mechanism of this disparity we examined the relationship of an unstable (labile) form of HbA1c (L‐HbA1c) with race and glucose. Methods Samples for HbA1c were collected from pediatric patients self‐identified as either AA (15F, 12M, age 13.4 ± 3.5 years) or EA (22F, 30M, age 14.6 ± 3.4 years) with type 1 diabetes at the time of a clinic visit. Clinic HbA1c (HbA1c) was performed by immunoassay. L‐HbA1c equaled the difference in the HbA1c fraction by dynamic capillary isoelectric focusing before and after incubation in a low pH buffer. A capillary glucose (Clinic‐BG) was measured at clinic visit. Mean blood glucose (MBG) was calculated from the last 30 days of the patient's glucose meter data. The influence of race on L‐HbA1c was assessed in a multiple variable regression model adjusted for Clinic‐BG. Results The groups were similar for age and duration of diabetes. L‐HbA1c was correlated with Clinic‐BG, MBG, and HbA1c. The mean levels of L‐HbA1c, HbA1c, MBG, but not Clinic‐BG were higher in AA patients compared to EA. After adjustment for Clinic‐BG, L‐HbA1c was still higher in AA (2.8 ± 0.7% AA vs 2.1 ± 0.7% EA, P < .0001). Conclusions L‐HbA1c is correlated with Clinic‐BG. At any given level of Clinic‐BG, AA patients have higher levels of L‐HbA1c than EA. This preliminary study suggests that early factors prior to the formation of stable HbA1c may contribute to the observed glucose‐independent racial disparity.

Insights on the pathogenesis of type 2 diabetes as revealed by signature genomic classifiers in an African American population in the Washington, DC area

“…The average HbA1c level in another AA population was comparatively higher than that of the Caucasian population 41 . HbA1c not only provides a reliable measure of chronic hyperglycemia but also correlates well with the risk of long‐term diabetes complications 42 .…”

“…The average HbA1c level in another AA population was comparatively higher than that of the Caucasian population. 41 HbA1c not only provides a reliable measure of chronic hyperglycemia but also correlates well with the risk of long-term diabetes complications. 42 The suboptimal management of HbA1C level is assumed to be caused by biological, socioeconomic, and quality-of-care-related variables.…”

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“…21,41,42 The concentrations of the biochemical precursor to clinically measured HbA1c, labile HbA1c, has also been found to be higher in NHB vs NHW youth, suggesting differences in the internal RBC environment as a possible underlying cause of this phenomenon. 43 Factors influencing HbA1c concentration such as variation in RBC indices and iron content do not appear to underlie MBG-independent racial disparity in HbA1c. 44,45 Some investigators have suggested differences in intracellular glucose, red cell longevity, and deglycating enzymes as possible mechanisms.…”