HbA1c Performance in African Descent Populations in the United States With Normal Glucose Tolerance, Prediabetes, or Diabetes

A Scoping Review

Lakshay Khosla, BA; Sonali Bhat, BA; Lee Ann Fullington, MPhil, MSLIS; Margrethe F. Horlyck-Romanovsky, DrPH

Disclosures

Prev Chronic Dis. 2021;18(3):e22 

In This Article

Abstract and Introduction

Abstract

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 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. We conducted a scoping review of US-based evidence documenting HbA1c 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. HbA1c 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 HbA1c test increased risk of false positives compared with White populations, regardless of glycemic status. Three studies of African Americans found that HbA1c of 5.7% to less than 6.5% or HbA1c of 6.5% or higher generally increased risk of overdiagnosis compared with OGTT or previous diagnosis. In one study of Afro-Caribbean people, HbA1c of 6.5% or higher detected fewer type 2 diabetes cases because of a greater risk of false negatives. Compared with OGTT, HbA1c tests in 4 studies of Africans found that HbA1c of 5.7% to less than 6.5% or HbA1c of 6.5% or higher leads to underdiagnosis.

Conclusion: HbA1c criteria inadequately characterizes glycemic status among heterogeneous African descent populations. Research is needed to determine optimal HbA1c cutoffs or other test strategies that account for risk profiles unique to African American, Afro-Caribbean, and African people living in the United States.

Introduction

People of African descent in the United States have a disproportionate burden of type 2 diabetes; prevalence is higher in African descent populations, 14%, compared with White populations of European descent (White populations), 9%.[1] Additionally, African descent populations are represented as a single group, despite being comprised of African American (91%), Afro-Caribbean (4.7%), and African (3.7%) people.[2,3] Limited evidence examines how intraethnic differences in cardiometabolic risk criteria, social determinants of health, and genetic admixture affect diabetes risk in these 3 populations.[4,5] Current glycated hemoglobin A1c (HbA1c) cutoffs (HbA1c 5.7% to less than 6.5% for prediabetes; HbA1c of 6.5% or higher for type 2 diabetes), determined from predominantly White population cohorts,[4–8] may perform suboptimally in evaluating glycemic status in this diverse population of African American, Afro-Caribbean, and African populations.[9–12] African American people may have higher HbA1c values across the glycemic spectrum,[9,13] and African immigrants may have lower HbA1c values compared with White people.[14] To ensure accurate detection of type 2 diabetes, there is a need to understand the ability of HbA1c to correctly classify type 2 diabetes status and to evaluate intraethnic variation among African American, Afro-Caribbean, and African people.[15–17]

Compared with random glucose, fasting plasma glucose (FPG), and the 2-hour oral glucose tolerance test (OGTT), HbA1c has multiple benefits. It does not require fasting, tracks plasma glucose over the preceding 2 to 3 months, and better predicts complications such as cardiovascular disease.[4,18] The HbA1c test is stable, unaffected by external variables (eg, exercise, recent meals, and environmental stressors), and easily added to blood tests.[19,20] However, interpretation of HbA1c results is affected by the reduced lifespan of red blood cells in patients with type 2 diabetes, anemia, and hemoglobinopathies, conditions which disproportionately affect African descent populations.[21–25]

The goal of our study was to conduct a scoping review of US-based peer-reviewed evidence documenting HbA1c performance in African American, Afro-Caribbean, and African populations in the United States with the objectives of 1) summarizing evidence on HbA1c performance in each subethnic group; 2) demonstrating variations in HbA1c performance by each subethnic group; and 3) identifying potential future areas of research.

Comments

3090D553-9492-4563-8681-AD288FA52ACE

processing....