Association of A1C and fasting plasma glucose levels with diabetic retinopathy prevalence in the U.S. population: Implications for diabetes diagnostic thresholds.
OBJECTIVE
To examine the association of A1C levels and fasting plasma glucose (FPG) with diabetic retinopathy in the U.S. population and to compare the ability of the two glycemic measures to discriminate between people with and without retinopathy.


METHODS
This study included 1,066 individuals aged >or=40 years from the 2005-2006 National Health and Nutrition Examination Survey. A1C, FPG, and 45 degrees color digital retinal images were assessed. Retinopathy was defined as a level >or=14 on the Early Treatment Diabetic Retinopathy Study severity scale. We used joinpoint regression to identify linear inflections of prevalence of retinopathy in the association between A1C and FPG.


RESULTS
The overall prevalence of retinopathy was 11%, which is appreciably lower than the prevalence in people with diagnosed diabetes (36%). There was a sharp increase in retinopathy prevalence in those with A1C >or=5.5% or FPG >or=5.8 mmol/l. After excluding 144 people using hypoglycemic medication, the change points for the greatest increase in retinopathy prevalence were A1C 5.5% and FPG 7.0 mmol/l. The coefficients of variation were 15.6 for A1C and 28.8 for FPG. Based on the areas under the receiver operating characteristic curves, A1C was a stronger discriminator of retinopathy (0.71 [95% CI 0.66-0.76]) than FPG (0.65 [0.60 - 0.70], P for difference = 0.009).


CONCLUSIONS
The steepest increase in retinopathy prevalence occurs among individuals with A1C >or=5.5% and FPG >or=5.8 mmol/l. A1C discriminates prevalence of retinopathy better than FPG.
Cheng
Yiling J
YJ
Division of Diabetes Translation, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, Atlanta, Georgia, USA. ycheng@cdc.gov.
Gregg
Edward W
EW
Geiss
Linda S
LS
Imperatore
Giuseppina
G
Williams
Desmond E
DE
Zhang
Xinzhi
X
Albright
Ann L
AL
Cowie
Catherine C
CC
Klein
Ronald
R
Saaddine
Jinan B
JB
D001786:Blood Glucose / Q000032:analysis*; D003925:Diabetic Angiopathies / Q000453:epidemiology; D003930:Diabetic Retinopathy / Q000453:epidemiology*; D005006:Ethnicity; D005215:Fasting; D005260:Female; D006442:Glycated Hemoglobin / Q000378:metabolism*; D006801:Humans; D006973:Hypertension / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D009749:Nutrition Surveys; D018579:Patient Selection; D015995:Prevalence; D044469:Racial Groups; D012680:Sensitivity and Specificity; D014481:United States / Q000453:epidemiology
D001786:Blood Glucose; D006442:Glycated Hemoglobin