A1C — a measure of long-term blood glucose control that can be used both to diagnose diabetes and to evaluate diabetes management — is a less reliable way to diagnose diabetes in people of African descent, according to a new analysis published in the journal Preventing Chronic Disease.
As the researchers pointed out, Black people — those of African descent — are often incorrectly viewed as a single group or ethnicity, when in fact a wide range of ethnicities are represented by this label. Recent studies have pointed to a variable link between A1C and more direct measures of blood glucose status — like an oral glucose tolerance test (OGTT) — among different groups of people of African descent in the United States. For this analysis, the researchers combined data from 12 recent studies to try to get a better picture of how A1C corresponds to glucose status in various groups of Black people.
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All of the studies included data on race or ethnicity, and compared A1C in people of African descent with A1C in other racial or ethnic groups, or looked at the relationship between A1C and the results of an OGTT, fasting plasma glucose, or a previous diabetes diagnosis. The researchers looked at the risk of A1C leading to either a false positive or false negative when it comes to diabetes or prediabetes status, as shown by the other measures.
A1C linked to false diagnosis positives and negatives in those of African descent
In five of the studies in the analysis, A1C was found to be linked to false positives for diabetes or prediabetes in African Americans, compared with white people. In addition, three of these five studies found that an A1C level of 5.7% up to 6.5%, or 6.5% or higher, increased the risk of overdiagnosing diabetes or prediabetes compared with an OGTT or previously known diabetes status.
But African Americans aren’t the whole story when it comes to people of African descent, as further studies included in the analysis made clear. In one study involving people of Afro-Caribbean descent, A1C was linked to a greater risk of false negatives in diabetes diagnosis, with a level of 6.5% or higher less likely to detect diabetes in this group. And for African people living in the United States, four studies found that A1C also leads to a higher risk of underdiagnosing diabetes.
More research is needed, the investigators noted, to find out how specific groups of people of African descent tend to respond to A1C as a measure used to diagnose diabetes. Specifically, they wrote, there may be a different optimal cutoff point to diagnose diabetes based on A1C for African American, Afro-Caribbean, and African people living in the United States. In the meantime, these findings may lead some doctors to use a measure other than A1C — such as an OGTT or fasting glucose level — to diagnose diabetes or prediabetes, or to double-check a diagnosis, among people of African descent when their A1C level is close to a cutoff for diagnosis.
Want to learn more about A1C? Read “How to Lower A1C Levels Naturally,” “How to Lower Your A1C Levels: More Steps You Can Take” and “What Is HbA1c?”
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