title: Should the hemoglobin A1c diagnostic cutoff differ between blacks and whites? A cross-sectional study.
abstract: BACKGROUND
  Hemoglobin A1c (HbA1c) levels are known to be consistently higher in black persons than in white persons at any given glycemic level. Whether the optimal diagnostic threshold of HbA1c should differ between blacks and whites is unclear.
  
  
  OBJECTIVE
  To compare the relationships between HbA1c level and the prevalence of retinopathy in black and white U.S. adults.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  A nationally representative sample of the National Health and Nutrition Examination Survey from 2005 through 2008.
  
  
  METHODS
  2804 white persons and 1008 black persons aged 40 years or older in the United States.
  
  
  METHODS
  Prevalence of retinopathy. Logistic regression models and restricted cubic spline models were constructed separately for white and black populations to test the HbA1c levels at which risk for retinopathy begins to increase.
  
  
  RESULTS
  After adjustment for age, sex, hypertension, body mass index, family history of diabetes, and use of antidiabetes medications or insulin, the lowest HbA1c category for which the prevalence of retinopathy was significantly higher than the reference category (&lt;5.5%) was 6.0% to 6.4% for white persons (risk difference, 4.8% [95% CI, 0.5% to 9.1%]) and 5.5% to 5.9% for black persons (risk difference, 5.3% [CI, 1.0% to 9.5%]). The restricted cubic spline models indicated that the risk for retinopathy increased at lower HbA1c levels in black persons than in white persons.
  
  
  CONCLUSIONS
  The cross-sectional design of the study precluded examining the effect of the duration at each HbA1c level.
  
  
  CONCLUSIONS
  The prevalence of retinopathy begins to increase at a lower HbA1c level in black Americans than in white Americans. The findings do not support increasing the diagnostic threshold of HbA1c in black persons.
  
  
  BACKGROUND
  None.
authors.affiliation: Beth Israel Deaconess Medical Center, 330 Brookline Avenue, Boston, MA 02215, USA. ytsugawa@bidmc.harvard.edu
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Tsugawa
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Mukamal
authors.forename: Roger B
authors.initials: RB
authors.lastname: Davis
authors.forename: William C
authors.initials: WC
authors.lastname: Taylor
authors.forename: Christina C
authors.initials: CC
authors.lastname: Wee
mesh_terms: D000328:Adult; D044383:Black People; D001786:Blood Glucose / Q000378:metabolism; D003430:Cross-Sectional Studies; D003930:Diabetic Retinopathy / Q000097:blood / Q000175:diagnosis* / Q000208:ethnology*; D005260:Female; D006442:Glycated Hemoglobin / Q000032:analysis / Q000378:metabolism*; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009749:Nutrition Surveys; D015995:Prevalence; D018570:Risk Assessment; D014481:United States / Q000453:epidemiology; D044465:White People; D001741:Black or African American
chemical_list: D001786:Blood Glucose; D006442:Glycated Hemoglobin