title: Glucose-independent, black-white differences in hemoglobin A1c levels: a cross-sectional analysis of 2 studies.
abstract: BACKGROUND
  A previous study of participants with prediabetes found that hemoglobin A(1c) (HbA(1c)) levels differed between black and white participants with no differences in glucose concentration.
  
  
  OBJECTIVE
  To determine whether black-white differences in HbA(1c) level are present in other populations and across the full spectrum of glycemia.
  
  
  METHODS
  Cross-sectional, retrospective.
  
  
  METHODS
  Outpatient.
  
  
  METHODS
  1581 non-Hispanic black and white participants between 18 and 87 years of age without known diabetes in the SIGT (Screening for Impaired Glucose Tolerance) study and 1967 non-Hispanic black and white participants older than 40 years without known diabetes in the NHANES III (Third National Health and Nutrition Examination Survey).
  
  
  METHODS
  HbA(1c) levels, anthropometry, and plasma glucose levels during oral glucose tolerance testing.
  
  
  RESULTS
  Hemoglobin A(1c) levels were higher in black than in white participants with normal glucose tolerance (0.13 percentage point [P < 0.001] in the SIGT sample and 0.21 percentage point [P < 0.001] in the NHANES III sample), prediabetes (0.26 percentage point [P < 0.001] and 0.30 percentage point [P < 0.001], respectively), or diabetes (0.47 percentage point [P < 0.020] and 0.47 percentage point [P < 0.013], respectively) after adjustment for plasma glucose levels and other characteristics known to correlate with HbA(1c) levels.
  
  
  CONCLUSIONS
  The mechanism for the differences is unknown.
  
  
  CONCLUSIONS
  Black persons have higher HbA(1c) levels than white persons across the full spectrum of glycemia, and the differences increase as glucose intolerance worsens. These findings could limit the use of HbA(1c) to screen for glucose intolerance, indicate the risk for complications, measure quality of care, and evaluate disparities in health.
authors.affiliation: Division of Endocrinology, Emory University School of Medicine, 49 Jesse Hill Jr. Drive SE, Atlanta, GA 30303, USA.
authors.forename: David C
authors.initials: DC
authors.lastname: Ziemer
authors.forename: Paul
authors.initials: P
authors.lastname: Kolm
authors.forename: William S
authors.initials: WS
authors.lastname: Weintraub
authors.forename: Viola
authors.initials: V
authors.lastname: Vaccarino
authors.forename: Mary K
authors.initials: MK
authors.lastname: Rhee
authors.forename: Jennifer G
authors.initials: JG
authors.lastname: Twombly
authors.forename: K M Venkat
authors.initials: KM
authors.lastname: Narayan
authors.forename: David D
authors.initials: DD
authors.lastname: Koch
authors.forename: Lawrence S
authors.initials: LS
authors.lastname: Phillips
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D044383:Black People; D001786:Blood Glucose / Q000378:metabolism*; D003430:Cross-Sectional Studies; D003920:Diabetes Mellitus / Q000097:blood / Q000208:ethnology; D005260:Female; D006442:Glycated Hemoglobin / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011236:Prediabetic State / Q000097:blood / Q000208:ethnology; D012189:Retrospective Studies; D044465:White People; D055815:Young Adult
chemical_list: D001786:Blood Glucose; D006442:Glycated Hemoglobin