Genetic Ancestry Markers and Difference in A1c Between African American and White in the Diabetes Prevention Program

Racial/ethnic and socioeconomic disparities in achievement of treatment goals within a clinical trial: a secondary analysis of the ACCORD trial

AIMS/HYPOTHESIS

Clinical trial participation should theoretically reduce barriers to care by ensuring medication and healthcare access. We aimed to evaluate disparities in achieving diabetes treatment targets by race/ethnicity and educational attainment within the Action to Control Cardiovascular Risk in Diabetes (ACCORD) trial (ClinicalTrials.gov NCT00000620).

METHODS

The ACCORD trial included three interventions of varying participant burden: glycaemic (high burden), blood pressure (medium burden) and triglyceride-lowering (low burden). We examined adjusted odds ratios (aORs) for achievement of glycaemic targets, blood pressure targets and a ≥25% reduction in triglyceride levels (a proxy for adherence to fenofibrate therapy) in the first year, and for hypoglycaemia requiring medical assistance at any time, by treatment arm, race/ethnicity and educational attainment using multivariable models adjusted for demographics and clinical characteristics. We explored whether disparities in glycaemic goal achievement were mediated by hypoglycaemia, medication use, change in BMI or number of study visits attended.

RESULTS

Compared with White participants, participants who identified as Black, Hispanic and Other race/ethnicity were less likely to achieve glycaemic targets (aOR [95% CI]) 0.63 [0.55,0.71], 0.73 [0.61, 0.88], 0.82 [0.71, 0.96], respectively); Black participants but not Hispanic and Other race/ethnicity participants were less likely to achieve blood pressure targets (aOR [95% CI] 0.77 [0.65, 0.90], 1.01 [0.78, 1.32], 1.01 [0.81, 1.26], respectively); and Black, Hispanic and Other race/ethnicity participants were equally or more likely to achieve triglyceride reduction (aOR [95% CI] 1.77 [1.38, 2.28], 1.34 [0.98, 1.84], 1.43 [1.10, 1.85], respectively). Differences in goal achievement by educational attainment were generally not significant after adjusting for baseline characteristics. Rates of hypoglycaemia requiring medical assistance were highest among Black individuals and those with lower educational attainment. Associations between race/ethnicity and glycaemic control were partially mediated by differences in insulin dosing and oral medication use.

CONCLUSIONS/INTERPRETATION

Racially/ethnically minoritised participants in the ACCORD trial were less likely to achieve high-burden (glycaemic) treatment goals but were generally similarly likely to achieve goals of less intensive interventions. Differences in glycaemic treatment goal achievement were partially mediated by differences in medication use but not mediated by hypoglycaemia, change in BMI or study visit attendance.

Racial and ethnic differences in circulating N-terminal pro-brain-type natriuretic peptide (NT-proBNP) in US adults

BACKGROUND

The presence and interpretation of racial and ethnic differences in circulating N-terminal pro-brain-type natriuretic peptide (NT-proBNP), a diagnostic biomarker for heart failure, are controversial.

OBJECTIVE

To examine racial and ethnic differences in NT-proBNP levels among the general US adult population.

METHODS

We performed a cross-sectional analysis of data from the 1999-2004 National Health and Nutrition Examination Survey (NHANES). We included 4717 non-Hispanic White, 1675 non-Hispanic Black, and 2148 Mexican American adults aged 20 years or older without a history of cardiovascular disease. We examined the associations of race and ethnicity with NT-proBNP using linear and logistic regression models in the overall population and in a younger, 'healthy' subsample.

RESULTS

The mean age was 45 years. Median NT-proBNP levels were significantly lower among Black (29.3 pg/mL) and Mexican American adults (28.3.4 pg/mL) compared to White adults (49.1pg/mL, P-values<0.001). After adjusting for sociodemographic factors and cardiovascular risk factors, NT-proBNP was 34.4% lower (95%CI -39.2 to -29.3%) in Black adults and 22.8% lower (95%CI -29.4 to -15.5) in Mexican American adults compared to White adults. Our findings were consistent in a young, healthy subsample, suggesting non-cardiometabolic determinants of these differences.

CONCLUSIONS

NT-proBNP levels are significantly lower among Black and Mexican American adults compared with White adults, independent of cardiometabolic risk. Although race/ethnicity is a poor proxy for genetic differences, our findings may have clinical implications for the management of HF. However, studies in diverse populations are needed to characterize the biological basis of NT-proBNP variation.

HbA1c 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_1c (HbA_1c) 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_1c 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_1c 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_1c test increased risk of false positives compared with White populations, regardless of glycemic status. Three studies of African Americans found that HbA_1c of 5.7% to less than 6.5% or HbA_1c of 6.5% or higher generally increased risk of overdiagnosis compared with OGTT or previous diagnosis. In one study of Afro-Caribbean people, HbA_1c of 6.5% or higher detected fewer type 2 diabetes cases because of a greater risk of false negatives. Compared with OGTT, HbA_1c tests in 4 studies of Africans found that HbA_1c of 5.7% to less than 6.5% or HbA_1c of 6.5% or higher leads to underdiagnosis.

Conclusion

HbA_1c criteria inadequately characterizes glycemic status among heterogeneous African descent populations. Research is needed to determine optimal HbA_1c cutoffs or other test strategies that account for risk profiles unique to African American, Afro-Caribbean, and African people living in the United States.

The Sickle Effect: The Silent Titan Affecting Glycated Hemoglobin Reliability

Hemoglobin A1c (HbA1c) is a popular invaluable tool in the diagnosis of Type 2 diabetes for red blood cells (RBCs) with a lifespan of 120 days; however, many factors, including hemoglobinopathies, affect its accuracy. Sickle cell trait, primarily a benign medical condition, is a point mutation in only one of two beta-globin genes on chromosome 11. We performed a traditional review to identify how the sickle cell trait (SCT) affects the interpretation of HbA1c and the further implications it may have on the diagnosis and management of Type 2 diabetes. A literature search was performed using PubMed®/MEDLINE® and Google Scholar with formulated keywords (sickle cell trait, HbAS, HbA1c, glycosylated hemoglobin, diabetes, RBC lifespan, race, and genetics), with the majority of results being mainly observational studies. The National Glycohemoglobin Standardization Program (NGSP) is responsible for standardizing HbA1c results and also highlights factors that can interfere with HbA1c, including hemoglobin variants. Studies that utilize only an NGSP-certified method with no clinically significant interference by HbS in patients with and without SCT showed contrasting results. Additional studies showed that persons of African ancestry, the group to which the majority of SCT patients belong, have a higher HbA1c than non-Hispanic whites (NHWs), just based on race, and a greater probability of having glucose-6-phosphate dehydrogenase (G6PD) deficiency, which lowers HbA1c. The most extensive study investigating the RBC lifespan in SCT patients showed a reduction in the cell lifespan compared to normal patients; however, other smaller studies were contradictory. Our study highlights the need for hemoglobinopathy detection before or during HbA1c measurement in populations with a high degree of African ancestry and the importance of patient notification. It also shows that SCT affects the accuracy of HbA1c, through its likely reduction of RBC lifespan and its increased association with African ancestry and G6PD deficiency. This review recommends that for SCT patients with potential Type 2 diabetes, HbA1c should be used in combination with another diagnostic tool such as fasting blood glucose, fructosamine, or glycated albumin to decrease the chances of a missed diagnosis.

Importance of Genetic Studies of Cardiometabolic Disease in Diverse Populations

Genome-wide association studies have revolutionized our understanding of the genetic underpinnings of cardiometabolic disease. Yet, the inadequate representation of individuals of diverse ancestral backgrounds in these studies may undercut their ultimate potential for both public health and precision medicine. The goal of this review is to describe the imperativeness of studying the populations who are most affected by cardiometabolic disease, to the aim of better understanding the genetic underpinnings of the disease. We support this premise by describing the current variation in the global burden of cardiometabolic disease and emphasize the importance of building a globally and ancestrally representative genetics evidence base for the identification of population-specific variants, fine-mapping, and polygenic risk score estimation. We discuss the important ethical, legal, and social implications of increasing ancestral diversity in genetic studies of cardiometabolic disease and the challenges that arise from the (1) lack of diversity in current reference populations and available analytic samples and the (2) unequal generation of health-associated genomic data and their prediction accuracies. Despite these challenges, we conclude that additional, unprecedented opportunities lie ahead for public health genomics and the realization of precision medicine, provided that the gap in diversity can be systematically addressed. Achieving this goal will require concerted efforts by social, academic, professional and regulatory stakeholders and communities, and these efforts must be based on principles of equity and social justice.

Evaluating the promise of inclusion of African ancestry populations in genomics

The lack of representation of diverse ancestral backgrounds in genomic research is well-known, and the resultant scientific and ethical limitations are becoming increasingly appreciated. The paucity of data on individuals with African ancestry is especially noteworthy as Africa is the birthplace of modern humans and harbors the greatest genetic diversity. It is expected that greater representation of those with African ancestry in genomic research will bring novel insights into human biology, and lead to improvements in clinical care and improved understanding of health disparities. Now that major efforts have been undertaken to address this failing, is there evidence of these anticipated advances? Here, we evaluate the promise of including diverse individuals in genomic research in the context of recent literature on individuals of African ancestry. In addition, we discuss progress and achievements on related technological challenges and diversity among scientists conducting genomic research.