HbA1c equally useful across ethnic groups

Published on October 26, 2012 at 5:15 PM · No Comments

By , medwireNews Reporter

Currently recommended clinical cutoff points for diabetes diagnosis using glycated hemoglobin (HbA1c) should be interpreted similarly in Whites, Blacks, and Hispanics, show findings from a US study.

"We found no evidence that ethnic group modified the relative association of HbA1c with prevalent retinopathy," say Elizabeth Selvin (Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA) and colleagues.

"These results should help alleviate concerns regarding the use of HbA1c for diagnosis and monitoring of diabetes in diverse populations."

Current clinical diagnostic categories for HbA1c are largely based on the established association between HbA1c and retinopathy as well as trials demonstrating that lowering HbA1c can reduce microvascular complications. However, recent studies have raised concerns that the performance of HbA1c may differ in certain subpopulations and that new recommendations might be problematic in individuals of non-European ancestry, explain Selvin et al.

In a cross-sectional analysis of 2945 non-Hispanic White people, 1046 non-Hispanic Black people, and 1231 Hispanic American individuals from the 2005-2008 NHANES (National Health and Nutrition Examination Survey), the researchers found that the mean HbA1c among those without diabetes was 5.5% in the White individuals, while it was 5.7% and 5.6% in Black and Hispanic individuals, respectively.

For those diagnosed with diabetes, the corresponding mean values for the ethnic groups were 6.9%, 7.5%, and 7.7%.

As reported in Diabetes Care, the prevalence of retinopathy was significantly higher in Black and Hispanic individuals compared with White individuals.

Among those with undiagnosed diabetes (HbA1c ≥6.5%), the prevalence of retinopathy was 9% in White people, compared with 19% and 22% in Black and Hispanic people, respectively, while the prevalence rates among those with diagnosed diabetes and HbA1c below 7% were 18%, compared with 25% and 16%, respectively.

The prevalence of retinopathy in those with diagnosed diabetes and an HbA1c level of at least 7% was 49% in Whites, 57% in Blacks, and 50% in Hispanics.

In addition, the proportion of individuals with more severe retinopathy was significantly higher among Black and Hispanic participants compared with White individuals.

The researchers report that HbA1c clinical categories were significantly associated with the prevalence of retinopathy. However, the magnitude of the association did not differ significantly by ethnic group and this remained the case whether HbA1c was modeled continuously or stratified by diabetes status.

The substantially higher prevalence of retinopathy in Black and Hispanic individuals compared with White people may partially reflect ethnic disparities in the diagnosis of diabetes and the management of hyperglycemia among individuals with diabetes, suggest Selvin and team.

"Overall our results support current recommendations for the use of HbA1c for diagnosis of diabetes, not only in nonHispanic white populations, but also for nonHispanic Black and Hispanic individuals," concludes the team.

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