Hemoglobin A1C results overestimated glycemia in African American patients with diabetes compared to White patients and patients of other race/ethnicities, which may lead to premature diabetes diagnoses, overtreatment, or incorrect assessments of diabetes health inequalities, according to a recent study published in Diabetes Technology & Therapeutics.

According to the study from Andrew J. Karter, PhD, from the division of research at Kaiser Permanente Northern California, and colleagues, while hemoglobin A1C is a commonly used marker to assess glycemic control in diabetes patients, research has shown that A1C levels can vary among different racial and ethnic groups, potentially leading to disparities in diabetes diagnosis and treatment.

“There is evidence that African American patients or minority patients … have higher A1Cs than White patients with the same mean glucose,” the researchers wrote. “This has public health consequences given even subtle A1C elevations could unintentionally lead to premature diabetes diagnoses, inappropriate treatment intensification, and biased assessment of quality of care and health inequities.”

To investigate the relationship between mean glucose levels, as measured by continuous glucose monitors (CGM), and A1C levels in a diverse group of diabetes patients, particularly focusing on differences across racial and ethnic backgrounds, Karter and colleagues conducted a retrospective analysis of data from 1,788 patients with diabetes who utilized CGM devices between 2016 and 2021 within the Kaiser Permanente healthcare system.

 In this population, a total of 5,264 A1C results were examined, and mean glucose levels were calculated based on 124,388,901 CGM readings captured during the 90 days preceding each A1C assessment. The researchers used hierarchical mixed models to estimate racial/ethnic disparities in the relationship between mean glucose levels and A1C.

The researchers found a significant disparity in A1C levels between African American and White patients with the same mean glucose levels. African American patients exhibited an A1C level that was, on average, 0.33 percentage points higher than their White counterparts (95% CI, 0.23-0.44; P < .0001). This discrepancy was statistically significant, highlighting that A1C levels in African American patients may overestimate their actual glycemia, which could potentially lead to premature diabetes diagnoses, overtreatment, or inaccurate assessments of health disparities.

In contrast, A1C results for Asian, Latino, and multiethnic patients were not significantly different from those of White patients when mean glucose levels were considered suggesting that the A1C-measured glycemic control was more accurate in these groups. The researchers also noted that the slope of the association between mean glucose and A1C did not significantly differ across racial and ethnic groups. This suggests that the impact of mean glucose levels on A1C values is relatively consistent among these groups.

The variance in the association between mean glucose and A1C was considerably greater within racial and ethnic groups (65%) compared to between these groups (9%). Shin and colleagues concluded that A1C results overestimate glycemia in African American patients compared to not only White patients, but patients of other race/ethnicities.

“This bias could lead to premature diabetes diagnoses, overtreatment, or incorrect assessments of diabetes health inequalities among African American patients. However, racial, or ethnic adjustment of A1C is not supported as most of the total variance in the mean glucose-A1C association is within, not between, racial and ethnic groups,” they wrote. “Treatment decisions driven by guideline-based A1C targets should be individualized and supported or replaced by direct assessments of glycemia.”

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Disclosures: Some authors declared financial ties to drugmakers. See full abstract for details. Karter is an employee of Kaiser Permanente.

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