Racial and individual variability in HbA1c–glucose relationship
medwireNews: Glycated hemoglobin (HbA1c) levels are higher for a given blood glucose level in Black patients with diabetes than they are in White people, shows a continuous glucose monitoring (CGM) study.
The finding also show marked variability in this relationship between people of the same race, which the researchers say “has been underappreciated and is likely to have more meaningful implications for the use of HbA1c for diagnosing diabetes, establishing management goals for a patients with diabetes, and assessing risk for complications than does the observed racial difference in the mean glucose–HbA1c relationship.”
Differences between individuals of the same race were large, with, for example, CGM levels in White participants ranging from 6.7 to more than 11.1 mmol/L for an HbA1c level of about 8.0%.
...collateral or alternative measures may be needed to assess mean glucose control in Black patients with diabetes.
The study participants underwent CGM for up to 12 weeks, revealing that the HbA1c level was, on average, 0.4% higher in the 104 African–American patients than the 104 White patients for any given mean glucose level. Black and White participants had HbA1c levels of 9.1% versus 8.3%, but only a 0.6 mmol/L difference in CGM levels, rather than the 1.33 mmol/L difference that the researchers say would be expected based on the equation generated from the A1c-Derived Average Glucose Study (ADAG), which was conducted in a mostly White population.
This difference was apparent both in patients younger than 18 years and in older patients. However, the relationship of glycated albumin and fructosamine with blood glucose did not vary by race.
“Our results provide the strongest evidence to date that nonglycemic factors partially account for the higher HbA1c levels observed in black persons with diabetes,” write Robin Gal (Jaeb Center for Health Research, Tampa, Florida, USA) and co-researchers in the Annals of Internal Medicine.
However, they stress that there was still a racial disparity in glycemic control, with average CGM levels being 10.6 mmol/L in Black participants versus 11.0 mmol/L in White patients.
The researchers conclude that “interpretation for a given patient requires knowledge of that patient's mean glucose–HbA1c relationship, exemplifying the need for personalized medicine.”
They suggest: “Obtaining CGM data at least once, preferably for 14 days, before measurement of HbA1c may be a useful clinical care consideration because for a given individual, it has been shown that the relationship between HbA1c level and mean glucose concentration is relatively stable.”
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