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Data fail to support change in diagnostic threshold of HbA1c in black Americans
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Results suggesting that the prevalence of retinopathy appears to increase at a lower HbA1c level in black patients with diabetes vs. white patients have led researchers to recommend against raising the diagnostic threshold of HbA1c in black patients.
Yusuke Tsugawa, MD, MPH, a primary care fellow at Beth Israel Deaconess Medical Center in Boston, and colleagues examined the difference between white (n=2,804) and black (n=1,008) patients in the United States, aged 40 years or older in a cross-sectional study of data from the National Health and Nutrition Examination Survey.
Tsugawa and colleagues used logistic regression models and restricted cubic spline models, adjusting for age, sex, hypertension, BMI and family history of diabetes.
Results showed that the lowest HbA1c category for which the prevalence of retinopathy was significantly higher than the reference category (<5.5%) was 6% to 6.4% for white patients vs. 5.5% to 5.9% for black patients.
Data also indicated that black patients were younger; more likely to be women; had higher HbA1c and fasting plasma glucose; were more likely to be diagnosed with diabetes; were more likely to be on antidiabetic medication or insulin; have higher blood pressure and BMIs; were more likely to be receiving antihypertensive medication; have a family history of diabetes; drink less alcohol; smoke; and be less educated.
Previous studies have provided evidence that HbA1c levels are consistently higher in black patients at any given underlying glycemic level than in white patients. The mechanisms behind this racial difference in HbA1c are unclear, and no consensus exists among experts regarding the decision to tailor diagnostic thresholds according to race. However, these data indicate a change in the diagnostic threshold of HbA1c would not benefit black patients, the researchers wrote.
They said longitudinal studies with larger patient populations are needed to understand whether a lower threshold of HbA1c should be considered for diagnosing patients with diabetes in this population.
Disclosure: Dr. Tsugawa reports no relevant financial disclosures. See the study for a full list of the researchers’ disclosures.
Perspective
Back to TopKathy Berkowitz, APRN, FNP-BC, CDE
Based on the findings in this study along with evidence previously published in the literature stating HbA1c levels are 0.2% to 0.4% higher in blacks than in whites at any given glycemic level, the authors understandably do not support increasing the diagnostic threshold of HbA1c in black persons.
The higher rates of retinopathy identified in blacks over the age of 40 at what is currently considered normal HbA1c levels may have important implications for the practicing clinician. Health providers may need to be more proactive in caring for their black patients by detecting and aggressively treating factors beyond glucose levels that contribute to retinopathy such as hypertension, abnormal renal function, offering effective support for smoking cessation and other healthy lifestyle interventions, and by recommending routine eye exams to detect retinopathy at its earliest stage.
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