HbA Performance in African Descent Populations in the United States With Normal Glucose Tolerance, Prediabetes, or Diabetes: A Scoping Review.

Introduction: 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 A (HbA) 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. We conducted a scoping review of US-based evidence documenting HbA performance to assess glycemic status among African American, Afro-Caribbean, and African people.

Methods: A PubMed, Scopus, and Cumulative Index to Nursing and Allied Health Literature (CINAHL) search (January 2020) yielded 3,238 articles published from January 2000 through January 2020. After review of titles, abstracts, and full texts, 12 met our criteria. HbA results were compared with other ethnic groups or validated against the oral glucose tolerance test (OGTT), fasting plasma glucose (FPG), or previous diagnosis. We classified study results by the risk of false positives and risk of false negatives in assessing glycemic status.

Results: In 5 studies of African American people, the HbA test increased risk of false positives compared with White populations, regardless of glycemic status. Three studies of African Americans found that HbA of 5.7% to less than 6.5% or HbA of 6.5% or higher generally increased risk of overdiagnosis compared with OGTT or previous diagnosis. In one study of Afro-Caribbean people, HbA of 6.5% or higher detected fewer type 2 diabetes cases because of a greater risk of false negatives. Compared with OGTT, HbA tests in 4 studies of Africans found that HbA of 5.7% to less than 6.5% or HbA of 6.5% or higher leads to underdiagnosis.

Conclusion: HbA criteria inadequately characterizes glycemic status among heterogeneous African descent populations. Research is needed to determine optimal HbA cutoffs or other test strategies that account for risk profiles unique to African American, Afro-Caribbean, and African people living in the United States.