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


Data Sources

In early January 2020, we searched PubMed, Scopus, and Cumulative Index to Nursing and Allied Health Literature (CINAHL) for peer-reviewed studies published between January 1, 2000, and January 1, 2020, by using complex search strings that were tested and developed in partnership with our institution's health sciences librarian (L.A.F.). The search string included medical subject headings (MeSH) terms and key words such as "African continental ancestry group," "African Americans," "Caribbean," and "West Indian" to describe population groups and "Glycated Hemoglobin A," "hemoglobin A1c," and "hba1c" to describe the testing indicator of interest for type 2 diabetes (Appendix).

Study Selection

Throughout the review process, we screened articles for studies meeting the following inclusion criteria:

  1. Articles were original studies published between January 2000 and January 2020, that evaluated HbA1c performance in African descent groups.

  2. Study populations included African Americans, Afro-Caribbeans, or Africans.

  3. Study participants were living in the United States.

  4. Study was a database analysis, epidemiologic study, or clinical study.

  5. HbA1c performance was reported specifically in one or more of the African descent groups.

  6. HbA1c performance was assessed in healthy populations or for screening or diagnosis of prediabetes or type 2 diabetes.

  7. HbA1c performance was assessed by statistical methods (eg, sensitivity, specificity, and positive predictive value), compared with other tests in the same population, or compared African descent populations to other racial groups.

During the study selection process, we included studies that compared various diabetes screening tests against HbA1c, including the OGTT, FPG, and glycated protein tests, to avoid excluding major findings. Although the OGTT is considered optimal for comparison, it is far more costly, resource intensive, and time consuming than the FPG and glycated protein tests;[6–8] additionally, research supports the use of other tests along with OGTT or in place of OGTT to enhance detection of diabetes.[7,18–22] Because African descent populations are less likely to be adequately represented in clinical research and simultaneously experience health care inequities,[4,19] we wanted to be inclusive of all the data, in comparison to HbA1c, that were available for the populations.

On the basis of the title and abstract review, we excluded articles that did not match the set inclusion criteria above (Figure). Two authors (L.K. and S.B.) conducted independent title and abstract reviews. In the full-text review, we excluded articles with insufficient data (eg, case studies), narrative reviews, and articles that fell under a previously set exclusion criterion not detected during the title and abstract review. Full-text articles for potential studies were reviewed by 2 authors (L.K. and S.B.) independently. When multiple exclusion criteria were met, we categorized the article by the exclusion criterion that appeared first in title, abstract, or full text review. A third author (M.H.R.) verified that the exclusion criteria were relevant throughout the article.


Flow diagram of the study selection process for glycated haemoglobin A1c (HbA1c) testing performance in African descent populations in the United States, using PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses). Studies were published January 1, 2000, to January 1, 2020.

During the identification process, 3,238 records were identified through database searching. In the screening phase, 3,081 records were screened after 157 duplicates were removed. Records were excluded by using a title and abstract review (n = 3,035) by the following exclusion criteria: topic was type 1 diabetes (n = 98); age was exclusively less than 19 years or greater than 64 years (n = 217); topic was animals or objects (n = 22); study was conducted outside the United States (n = 422), study generalized African descent populations as one group (n = 58); study did not report HbA1c performance in African descent populations (n = 631); topic was a dietary study (n = 30); topic was other diseases, disorders, complications (including diabetes-related complications), or illnesses (eg, kidney) (n = 933); topic was a treatment or interventional study (n = 527); topic was gestational diabetes (n = 13); or topic was a genetic study (n = 84). After this screening process, the remaining 46 full-text articles were assessed for eligibility. Of these, 34 full-text articles were excluded based on the following exclusion criteria: insufficient data (n = 6); being a narrative review (n = 10); or for a reason not previously detected in the title or abstract (n = 18). The inclusion stage yielded 12 studies to be included in qualitative synthesis.

Data extraction

We created a data extraction sheet to record the study author and name, populations (sample size, male/female breakdown, race/ethnicity distribution, age, and study location), HbA1c laboratory methods, study design, HbA1c evaluation methods, findings, and HbA1c performance. We successfully retrieved any missing information by 1) searching through cited articles from which the studies retrieved data; 2) identifying parent studies and protocol descriptions given in prior publications; and 3) emailing corresponding authors. HbA1c performance was classified using 2 labels: 1) greater risk of false positive (GRFP) label indicated that the HbA1c test may result in overdetection of glycemic status (eg, type 2 diabetes) that the study is measuring or 2) greater risk of false negatives (GRFN) label indicated that the HbA1c test may result in underdetection of glycemic status. This classification system (GRFP or GRFN) was based on text analysis of the language used by the authors of each study in the way they interpreted their results (eg, lower sensitivity, lower specificity, more misdiagnoses). This allowed for standardization of labeling findings from different study designs. GRFP was assigned if studies reported 1) higher HbA1c values in African descent participants compared with other ethnic groups (eg, White participants) at the same glycemic level; 2) lower sensitivity because of less true positives; or 3) lower specificity because of more false positives. GRFN was assigned if studies reported 1) lower HbA1c values in participants compared with other ethnic groups at same glycemic level; 2) lower sensitivity because of more false negatives; or 3) or lower specificity because of less true negatives. Discrepancies in the review process and data extraction were resolved with input from a third author (M.H.R.).

Included studies were grouped based on study population (African American, Afro-Caribbean, and African) and then organized in alphabetical order by the first author's last name. Studies were labeled numerically as 1 through 12 based on this ordering.