When diagnosing diabetes or prediabetes, the A1c value in people of African origin varies depending on their ethnicity, as new research shows.
Results of a meta-analysis by Lakshay Khosla, BA, and colleagues from 12 US studies were published online March 11 in Preventing Chronic Disease.
The studies evaluated the use of the recommended A1c limits for diagnosing diabetes and prediabetes in Americans of African (African American), Afro-Caribbean, and African (African) immigrant descent. Overall, the currently used limits of 6.5% or more for diabetes and 5.7% to 6.5% for prediabetes tended to overestimate glycemia in African Americans and underestimate it in Afro-Caribbean and Africans.
“We recommend the use of A1c and fasting plasma glucose [FPG ] or better yet, a 2 hour oral glucose tolerance test [OGTT]”Senior author Margrethe F. Horlyck-Romanovsky, Dr. is a better test … the idea is to use two different tests instead of repeating one test,” she said.
The limitations of using A1c to assess glycemic status in people with certain nutritional deficiencies, anemia, or genetic hemoglobinopathies, including sickle cell traits, have been well described.
However, recent data suggests that A1c underperforms in people of African descent without these conditions, and few studies have looked at differences across sub-ethnic groups.
These problems are mentioned in the American Diabetes Association (ADA) guidelines for diagnosing diabetes. The ADA recommends “for patients with a hemoglobin variant but normal red blood cell turnover, such as patients with sickle cell traits, use an A1C test without interference from hemoglobin variants”.
Horlyck-Romanovsky commented, “We now know that the risk of diabetes is one of the intergenerational risks that are transmitted. Once we can demonstrate that the current tools are not working particularly well at detecting what we believe we are detecting,” Horlyck-Romanovsky commented. then.” we need to reevaluate and rethink it instead of continuing to say that it is working well. “
M. Sue Kirkman, MD, professor of medicine and medical director of the clinical trials division of the Diabetes Care Center at the University of North Carolina at Chapel Hill, told Medscape Medical News, “There are three different tests that can be used to diagnose diabetes.” and we knew they didn’t exactly identify the same people. Whatever you say is the gold standard, the others will look less sensitive or less specific. “
Kirkman, senior vice president of medical affairs for the ADA and chair of the committee that developed the first US guidelines for the use of A1c in diagnosing diabetes in 2009, said that while OGTT is often considered the gold standard because it was on most sensitive, its use can lead to overdiagnosis compared to FPG. “When A1c is included in the mix, that’s an extra part of the Venn diagram … they don’t completely overlap. You will see differences between the three tests even if you leave out the racing problem,” she said.
In addition, Kirkman said that while studies using continuous glucose monitoring have shown no differences between average A1c levels and average interracial glucose levels, “when you look at individuals, there is much more variation between individuals than between them . ” Blacks on average and whites on average. So it’s very complicated. “
Despite its limitations, Kirkman advised continued use of A1c because it is most effective at predicting long-term complications regardless of breed. “We know that blacks are more likely to develop diabetes and develop many of the complications of diabetes than whites.”
Regarding using another confirmatory test, Kirkman said it might be useful for people whose conditions are on the border between glycemia categories. “If their A1c is 8.5% and repeated they don’t need another test. But I’m thinking of the edges with glucose or A1c, keep an eye on them. If the A1c is 6.6% it might make sense to others to do tests to see, “she said.
Kirkman also warned generally against categorizing patients by race. She referred to the recent controversy surrounding the use of a race modifier in the estimated glomerular filtration rate (eGFR) formula, which appears to make people of African descent less likely to be eligible for kidney transplants and other nephrological treatments.
“I think we have to be careful when we say we need to make race corrections for A1c because then are we going to run into the same problem that we have with eGFR? … There are biracial people and just completely different genetics even within the same race. It’s going to be very exhausting and complicated … Will we have a different A1c limit if you’re African American, Caribbean, or moved here from Africa? It can get a bit ridiculous. “
Horlyck-Romanovsky agrees that it’s complicated.
“We’re using a social construct to compare the clinical outcomes. We really need to think about the heterogeneity within these racial groups that we consider monolithic. Human heritage is a story of admixture … Genetics only indicates what.” We are at risk, not from what we have. “
A1c differs between Africans, African American, and Afro-Caribbean
From the meta-analysis reported by Khosla of the College of Medicine at SUNY Downstate Health Sciences University in New York City and colleagues, seven of the 12 studies analyzed A1c performance in African Americans. four analyzed A1c performance among Africans; and they analyzed the performance in Afro-Caribbean. The study populations ranged from 83 to 16,056 participants, and the mean age of the participants was reportedly between 37 and 64 years.
The studies compared A1c performance in people of African descent with either other races (i.e. whites), with the 2-hour OGTT, FPG, and / or earlier diagnosis in the same people.
In five studies of African American people, the A1c test was associated with a higher risk of false positive results, assessed by either OGTT or FBG compared to whites over a range of glycemia levels. In one of these studies, the risk was also higher compared to Hispanic people.
In two of the studies, using an A1c level of 6.5% or greater in African Americans led to an overdiagnosis of type 2 diabetes compared to OGTT results. Another showed that African Americans can be overdiagnosed with prediabetes at A1c levels of 5.7% to 6.4%. Another study showed that an A1c value of less than 5.7% does not rule out the possibility of a diagnosis of type 2 diabetes.
In contrast, in one study with Afro-Caribbean people, the A1c limit of 6.5% or higher was associated with a higher risk of false negative results when using FPG as the diagnostic standard. In this study, more participants were accurately diagnosed with type 2 diabetes with an A1c cutoff of 6.26% or higher.
In African-born adults now living in the United States, outcomes were more similar to those in the Afro-Caribbean group: across the four studies, A1c was associated with a higher risk of false negative results for prediabetes with limits from 5.7% to 6 , 4% and for type 2 diabetes at a cutoff of 6.5% or more compared to OGTT results.
The study was funded by the National Institutes of Health. The authors have not disclosed any relevant financial relationships. Kirkman receives NIH funding and is a consultant for Encore Medical Education.
Prev Chronic Dis. Published online March 11, 2021. Full text
Miriam E. Tucker is a freelance journalist based in the Washington DC area. She is a regular contributor to Medscape. Additional work appears in the Washington Post, NPR blog Shots, and Diabetes Forecast magazine. She can be found on Twitter @MiriamETucker.
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