Glycemic thresholds for diabetes-specific retinopathy: implications for diagnostic criteria for diabetes.
OBJECTIVE
To re-evaluate the relationship between glycemia and diabetic retinopathy.


METHODS
We conducted a data-pooling analysis of nine studies from five countries with 44,623 participants aged 20-79 years with gradable retinal photographs. The relationship between diabetes-specific retinopathy (defined as moderate or more severe retinopathy) and three glycemic measures (fasting plasma glucose [FPG; n = 41,411], 2-h post oral glucose load plasma glucose [2-h PG; n = 21,334], and A1C [n = 28,010]) was examined.


RESULTS
When diabetes-specific retinopathy was plotted against continuous glycemic measures, a curvilinear relationship was observed for FPG and A1C. Diabetes-specific retinopathy prevalence was low for FPG <6.0 mmol/l and A1C <6.0% but increased above these levels. Based on vigintile (20 groups with equal numbers) distributions, glycemic thresholds for diabetes-specific retinopathy were observed over the range of 6.4-6.8 mmol/l for FPG, 9.8-10.6 mmol/l for 2-h PG, and 6.3-6.7% for A1C. Thresholds for diabetes-specific retinopathy from receiver-operating characteristic curve analyses were 6.6 mmol/l for FPG, 13.0 mmol/l for 2-h PG, and 6.4% for A1C.


CONCLUSIONS
This study broadens the evidence based on diabetes diagnostic criteria. A narrow threshold range for diabetes-specific retinopathy was identified for FPG and A1C but not for 2-h PG. The combined analyses suggest that the current diabetes diagnostic level for FPG could be lowered to 6.5 mmol/l and that an A1C of 6.5% is a suitable alternative diagnostic criterion.
Boden Institute of Obesity, Nutrition, and Exercise, University of Sydney, Sydney, Australia. stephen.colagiuri@sydney.edu.au
Stephen
S
Colagiuri
Crystal M Y
CM
Lee
Tien Y
TY
Wong
Beverley
B
Balkau
Jonathan E
JE
Shaw
Knut
K
Borch-Johnsen
D000328:Adult; D000368:Aged; D001786:Blood Glucose / Q000032:analysis; D003930:Diabetic Retinopathy / Q000097:blood* / Q000175:diagnosis / Q000378:metabolism; D005215:Fasting / Q000097:blood; D006442:Glycated Hemoglobin / Q000378:metabolism; D006801:Humans; D008875:Middle Aged; D055815:Young Adult
D001786:Blood Glucose; D006442:Glycated Hemoglobin