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


Prev Chronic Dis. 2021;18(3):e22 

In This Article


Of the 12 articles that met the inclusion criteria, studies numbered 1 through 7 analyzed HbA1c performance among African American people,[26–32] study number 8 analyzed HbA1c performance among Afro-Caribbean people,[33] and studies numbered 9 through12 analyzed HbA1c performance among African people.[34–37] All studies were conducted with people living in the United States (Table 1).

The population size of the studies varied from 83 to 16,056 participants, with the sex representation ranging from 69% male/31% female to 0% male/100% female (Table 1). The study cohorts consisted of 20.2% to 100% African descent populations. The overall age range across the different studies was 18 to 92 years and the mean age was between 37 and 64 years when reported (Table 1).

HbA1c laboratory analysis methods were high performance liquid chromatography (HPLC) for studies 1, 2, 4, 5, and 9 through 12,[26,27,29,30,34–37] or immunoassays for studies 3 and 6 through 8[28,31–33] (Table 1).

The study designs included either clinical data collection (studies 1 and 5 through 12)[26,30–37] or analyses of established databases (studies 2 through 4),[27–29] with publication dates ranging from 2010 to 2019 (Table 1). Study 1 was a retrospective study of patients who underwent HbA1c testing from May 2008 to February 2009 (Table 1).[26] Study 2 was a cross cross-sectional analysis within the longitudinal Coronary Artery Risk Development in Young Adults (CARDIA) study (Table 1).[27]

In these studies, HbA1c performance was evaluated by comparing HbA1c results in African descent populations to HbA1c results in other ethnic groups (eg, White people) (studies 1, 2, 5, and 7),[26,27,30,32] evaluating HbA1c test results against the 2-hour OGTT, FPG, glycated plasma proteins test results, or previous diagnosis in the same participants (studies 3, 6, and 8–12),[28,31,33–37] or both (study 4)[29] (Table 2). Studies conducted among African American people showed that the HbA1c test almost always had a GRFP in this population. Studies 1, 2, 4, 5, and 7 demonstrated that HbA1c values were higher in African Americans when compared with Whites across a range of glycemic states.[26,27,29,30,32] Additionally, Study 7 showed that HbA1c values were higher in African American people when compared with both White people and Hispanic people, leading to the potential of overdiagnosis of type 2 diabetes in African American people.[32] Using OGTT as a standard test for diagnosis of glycemic status, studies 4 and 6 demonstrated that using HbA1c results in overdiagnosis of type 2 diabetes when HbA1c is 6.5% or higher.[29,31] Study 3 showed that African American people may experience an overdiagnosis of prediabetes or type 2 diabetes at HbA1c of 5.7% to less than 6.5%; however, study 6 showed that an HbA1c cutoff of less than 5.7% does not eliminate the possibility of a type 2 diabetes diagnosis[28,31] (Table 2).

In the Afro-Caribbean population, HbA1c testing at the 6.5% or higher cutoff has a GRFN.[33] Using FPG as a standard for diagnosis of type 2 diabetes, study 8 showed that more participants were correctly diagnosed as having type 2 diabetes if the cutoff was lowered to 6.26% or higher, suggesting that HbA1c values are generally lower in Afro-Caribbean people (Table 2).

The Africans in America studies 9 through 12 all showed that HbA1c has a GRFN in African people at the HbA1c cutoff of 5.7% to less than 6.5% for prediabetes and HbA1c cutoff of 6.5% or higher for type 2 diabetes.[34–37] Using OGTT as a diagnostic standard for glycemic status, studies 9 through 12 demonstrated that using an HbA1c cutoff of 5.7% to less than 6.5% will lead to underdiagnosis of prediabetes in Africans. Additionally, study 9 showed that using an HbA1c cutoff of 6.5% or higher will lead to an underdiagnosis of type 2 diabetes in Africans[34] (Table 2).