Glucose-independent, black-white differences in hemoglobin A1c levels: a cross-sectional analysis of 2 studies.
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.
Ziemer
David C
DC
Division of Endocrinology, Emory University School of Medicine, 49 Jesse Hill Jr. Drive SE, Atlanta, GA 30303, USA.
Kolm
Paul
P
Weintraub
William S
WS
Vaccarino
Viola
V
Rhee
Mary K
MK
Twombly
Jennifer G
JG
Narayan
K M Venkat
KM
Koch
David D
DD
Phillips
Lawrence S
LS
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
D001786:Blood Glucose; D006442:Glycated Hemoglobin