African descent populations in the United States have high rates of type 2 diabetes and are incorrectly represented as a single group. Current glycated hemoglobin A1c (HbA1c) cutoffs (5.7% to <6.5% for prediabetes; ≥6.5% for type 2 diabetes) may perform suboptimally in evaluating glycemic status among African descent groups. When used to diagnose diabetes or prediabetes, the A1c level performs differently among persons of African descent, depending upon their specific ethnicity, new research suggests.

A scoping review of US-based evidence documenting HbA1c performance to assess glycemic status among African American, Afro-Caribbean, and African people was done. Findings from a meta-analysis by Lakshay Khosla, B.A., and colleagues of 12 U.S. studies were published online on March 11 in Preventing Chronic Disease.

The studies evaluated the use of recommended A1c cutoff levels to diagnose diabetes and prediabetes among Americans descended from African people (African Americans), Afro-Caribbean people, and people who immigrated from Africa (Africans). Overall, the currently used cutoff levels of 6.5% or higher for diabetes and 5.7% to 6.5% for prediabetes tended to overestimate glycemia in African Americans and underestimate it in Afro-Caribbean and African people. For African people, underdiagnosis of prediabetes and type 2 diabetes is also likely at the standard HbA1c cutoffs because diagnosis was missed by HbA1c despite being detected by oral glucose tolerance test [OGTT].

From the results, it was suggested that we use both A1c and fasting plasma glucose [FPG ] or, better yet, a 2-hour oral glucose tolerance test [OGTT].

Preventing Chronic Disease – SYSTEMATIC REVIEW — Volume 18 — March 11, 2021